.3 


COLORADO. 


of 


COLORADO. 


J.  S.   l 


GEORGETOWN,  COLO. 

GEORGETOWN    COURIER     PRINT. 

1887. 


•3 


Bancroft  Library 


INTRODUCTORY. 


In  the  preparation  of  this  glossary,  the  compiler  has  depended  largely 
upon  the  works  of  J.  D.  DANA  for  a  description  of  the  mineral  species,  except 
in  cases  where  the  local  mineral  has  undergone  examination.  He  has  also 
obtained  much  valuable  information  from  papers  upon  particular  minerals, 
read  before  scientific  associations,  and  from  articles  prepared  for  the  scientific 
press. 

From  a  mineralogical  point  of  view  the  wealth  of  Colorado  exceeds  that  of 
the  other  States.  In  the  metallic  minerals  almost  every  variety  has  been 
found  here.  And  doubtless  many  interesting  minerals  have  been  overlooked 
from  causes  that  it  is  impossible  to  guard  against.  The  immense  size  of  the 
mineral  region,  the  exceedingly  superficial  examination,  the  vast  area  yet 
unexplored,  and  the  absence  of  scientific  knowledge  on  the  part  of  those  whose 
discoveries  were  only  prompted  by  the  unusual  appearance  of  minerals,  have 
led  to  overlooking  many  that  are  of  value  to  the  scientist  and  commerce. 

Many  minerals  given  are  common  to  several  localities  in  the  State,  but, 
as  observed,  non-exploration  has  prevented  a  complete  knowledge  of  their 
locations.  To  make  subsequent  editions  of  this  work  more  complete,  the  com- 
piler solicits  the  aid  of  the  reader.  Any  information  regarding  localities  of 
minerals  will  be  greatly  appreciated,  and  where  tht  variety  of  a  mineral  is 
in  doubt,  specimens  sent  will  be  investigated. 

The  compiler  is  under  special  obligations  to  Mr.  WHITMAN  CROSS  and 
Mr.  W.  B.  SMITH,  of  the  U.  S.  Geological  Survey,  for  valuable  information. 

The  following  are  titles  of  the  works  referred  to  in  the  following  pages  : 

Proceedings  of  the  Colorado  Scientific  Society. 

Proceedings  of  the  Academy  of  Natural  Science,  Philadelphia. 

Proceedings  of  the  American  Philosophical  Society,  Philadelphia. 

American  Journal  of  Science. 

American  Chemical  Journal. 

Bulletins  of  the  U.  S.  Geological  Survey. 


J.  S.  RANDALL. 


GEORGETOWN,  COLORADO, 
January,  1887. 


MINERALS  OF  SOLORADO, 


GOLD. 

Crystallizes  in  the  Isometric  system  ;  the  octahedron  and  dodecahedron 
are  the  most  common  forms ;  sometimes  in  cubes  and  trapezohedrons ; 
the  crystals  are  usually  small  and  imperfect,  and  sometimes  elongated ; 
also  reticulated,  arborescent  and  spongiform  shapes,  in  scales  and  rolled 
masses.  Color  various  shades  of  gold-yellow,  sometimes  inclining  to  sil- 
ver-white. Very  ductile  and  malleable.  Hardness  2*5  to  3.  Specific  grav- 
ity 19'34  when  quite  pure. 

Occurs  in  greater  or  less  quantities  throughout  the  moun- 
tainous portions, of  the  State  in  the  gravel  of  streams  and  in 
veins.  The  veins  of  Gilpin  County  are  especially  noteworthy 
for  the  amount  of  gold  mined  annually.  Small  but  unique 
crystals  have  been  found  in  a  number  of  the  mines.  Large 
masses  of  wire  and  leaf  gold  were  taken  from  the  Printer 
Boy  mine,  in  Lake  County,  in  1870.  In  combination  with 
tellurium  in  many  of  the  mines  in  Boulder  County. 

SILVER. 

Isometric  ;  occurs  crystallized  in  cubes,  octahedrons,  trapezohedrons  and 
other  forms,  but  generally  distorted ;  usually  filiform,  arberescent,  in 
plates  or  coatings  and  sometimes  massive.  Color  silver-white,  but  subject 
to  tarnish.  Ductile.  Hardness  2'5-3.  Gravity  10'5  when  pure. 

Found  native  in  small  quantities  in  nearly  all  silver  mines 
in  the  State.  In  scales,  arborescent  and  filiform,  the  threads 
sometimes  knotting  a  mass  two  inches  in  diameter,  in  the 
mines  of  Georgetown.  Occasionally  found  in  nuggets  from 
the  size  of  a  pea  to  those  weighing  a  pound.  The  Boulder 
Nest  mine  in  Clear  Creek  County,  and  the  Caribou  mine  in 
Boulder  County  were  especially  productive  of  native  silver  in 
their  surface  workings.  Frequently  found  in  the  Blue 
Kiver  placers.  Crystals  are  very  seldom  met  with. 

MERCURY.     Quicksilver. 

Isometric ;  Occurs  in  small  fluid  globules.  Color  tin-white.  Lustre  me- 
tallic. 

Has  been  found  sparingly  in  the  tellurium-bearing  mines 
of  Boulder  County. 


6  Minerals  of  Colorado. 

NATIVE    COPPER. 

Isometric ;  occurs  crystallized  in  numerous  and  often  compound  forms ; 
often  filiform  and  arborescent ;  also  massive.  Color  copper-red.  Streak 
metallic  shining.  Ductile  and  malleable.  H.  2'5-3.  G.  8'94.  Usually 
found  alloyed  with  some  copper,  bismuth,  etc. 

At  the  head  of  Hand-Cart  Gulch,  where  it  was  mined  in 
early  days  under  the  supposition  that  it  was  gold.  Occurs  in 
small  quantities  in  the  mines  of  Central  City.  Quite  large 
quantities  of  wire  copper  have  heen  found  iu  the  Pittsburg 
mine  at  Empire.  Dendritic  coatings  found  in  the  Centennial 
mine,  Georgetown.  Loose  masses  have  been  found  in  the 
soil  near  Idaho  Springs.  Quite  abundant  in  the  copper  lodes 
near  Golden,  where  it  occurs  in  seams  from  J  to  one  inch  in 
thickness. 

NATIVE   BISMUTH. 

Hexagonal ;  occurs  in  rhombohedrons  nearly  approaching  the  cube ;  also 
reticulated  and  arborescent  shapes ;  foliated  and  granular.  Color  silver- 
white  with  a  reddish  tinge,  but  subject  to  tarnish.  Cleavable.  Sectile. 
Brittle  when  cold,  but  somewhat  malleable  when  heated.  H.  2-2*5.  G. 
9-72. 

Small  nuggets  of  native  bismuth  are  frequently  found  in 
the  placers  of  French  Gulch,  Summit  county.  Occasionally 
found  in  the  Las  Animas  mine,  Boulder  county,  associated 
with  bismutite  and  bismuthinite.  Specimens  in  collection  of 
J.  S.  Randall.  Bismuth  is  used  extensively  in  the  arts  and 
in  medicine;  with  antimony  in  the  construction  of  the  most 
sensitive  thermometers;  with  mercury  for  silvering  glass;  the 
sub-nitrate  is  used  for  enameling  porcelain,  and  in  gilding; 
in  the  manufacture  of  porcelain  and  optical  glass ;  the  nitrate 
is  used  in  dyeing  lilac  and  violet  in  calico  printing. 

NATIVE    TEULURIUM. 

Hexagonal;  occurs  in  six-sided  prisms  with  the  terminal  edges  re- 
placed by  single  planes;  generally  massive  and  granular.  Color  tin- 
white.  Lustre  metallic.  H.  2-2'5.  G.  6'l-6'3.  Usually  carries  some 
gold. 

Found  in  the  mines  of  Boulder  county,  associated  with 
other  tellurium  minerals.  A  few  crystals  have  been  found 
nearly  an  inch  long.  Specimens  in  compiler's  collection. 
Tellurium  has  no  use  in  the  arts,  and  is  valuable  only  for  its 
gold  and  silver  contents. 

NATIVE    SULPHUR. 

Orthorhombic  ;  the  prevailing  form  of  crystal  is  an  acute  octahedron,  com- 
posed of  two  four-sided  pyramids  with  rhombic  bases;  usually  occurs  in 
masses,  sometimes  consisting  of  concentric  coats.  Color  sulphur-yellow, 
sometimes  reddish  or  brown.  Lustre  resinous.  Transparent  to  subtrans- 
,  lucent.  H.  1-5-2-5.  G.  2;072. 

Abundant  about  the  mud  volcanoes  in  the  southwestern 
part  of  the  State. 


Minerals  of  Colorado.  8 

JAROSITE.  Sulphate  of  Iron.  G.  A.  Konig,  Proc.  Acad.  Nat.  Sci.,Phila. 
Khombehedral ;  occurs  in  crystals ;  also  massive  granular,  fibrous,  as  nod- 
ules and  as  an  incrustation.  H.  2'5.  G.  3'5.  Color  ochre-yellow,  amber- 
yellow  to  dark  brown.  Lustre  resinous  to  adamantine.  Analysis  by  Konig 
of  mineral  from  Iron  Arrow  mine:  sulphuric  acid  28'57,  sesquioxyd  of 
iron  51'10,  water  10'26,  potassa  7'13,  and  a  little  soda  and  silica. 

Found  in  minute  brilliant  crystals  in  the  Iron  Arrow  mine, 
Chaffee  county. 

ANGUESIXE.     Sulphate  of  Lead. 

Orthorhombic ;  occurs  in  rhombic  prisms  which  assume  the  general  form 
of  the  octahedron  when  short;  often  in  slender  implanted  crystals;  also 
occurs  massive;  lamellar  or  granular.  Color  gray,  white,  yellowish  or 
slightly  green.  Lustre  adamantine,  inclining  to  resinous.  Transparent  to 
opaque.  H.  3.  G.  6.  Comp.,  oxide  of  lead  73'6,  sulphuric  acid  26'4. 

In  the  Freeland  mine,  Clear  Creek  county,  in  aggregations 
of  grayish  translucent  crystals  about  the  size  of  a  grain  of 
wheat.  In  many  of  the  Leadville  mines  in  small  crystals  and 
in  crystalline  masses.  A  product  of  the  decomposition  of 
galena. 

ISICCOWTB.     Arsenical  Nickel. 

Hexagonal ;  rarely  occurs  crystallized  ;  usually  massive,  sometimes  reni- 
form  with  a  columnar  structure.  H.  5-5'5.  G.  7'33-7'67.  Lustre  metallic. 
Color  pale  copper-red,  with  a  gray  or  black  tarnish.  Streak  pale  brown- 
ish-black. Comp.,  arsenic  55*9,  nickel  44*1. 

Gem  mine,  on  Pine  Creek,  Fremont  county,  associated 
with  bornite  and  pyritiferous  minerals,  in  dolomite  gangue. 
Produces  annabergite  on  alteration  (Cross).  In  the  mines  at 
Silver  Cliff  (G en th).  Sparingly  in  the  Rosa  mine,atL)umont, 
Clear  Creek  county. 

]tlBI*O*?ITK*     Tellnride  of  Nickel.  _  W.  F.  Hillebrand,  Proc.  Cbl.Sc.Soc. 

Hexagonal ;  generally  occurs  in  indistinct  granular  and  foliated  par- 
ticles. Lustre  metallic.  Color  reddish-white,  rarely  tarnished  brown. 
Comp.,  tellurium  76'49,  nickel  23'51. 

Occurs  in  the  Forlorn  Hope  mine,  Boulder  county,  in  crys- 
talline forms,  associated  with  other  tellurides.  Specimens 
in  collection  of  Colorado  Scientific  Society.  A  rare  mineral, 
heretofore  found  only  in  California. 

PHBNACITB.     Silicate  of  Glucina.     W.  Cross,  Am.  Jr.  Sc.,  Oct.,  1882. 

Rhombohedral ;  crystals  occasionally  oblong,  but  generally  obtuse.  Color- 
less or  bright  wine-yellow  inclining  to  red ;  lustre  vitreous ;  transpa- 
rent to  opaque ;  double-refracting.  H.  7'5-8.  G.  3.  Comp.,  silica  54'2, 
glucina  45'8.  Resembles  quartz. 

At  Crystal  Park,  El  Paso  county,  in  cavities  in  granite, 
with  topaz,  zircon,  microcline,  albite,  smoky  quartz  and  li- 
monite  in  large,  broken  crystals.  At  Florissant  in  small,  flat 
crystals  upon  amazonstone  with  albite,  gothite  and  smoky 
quartz.  Specimens  in  collection  of  "Whitman  Cross,  Denver. 


Minerals  of  Colorado. 

Arsenide  of  Cobalt.  W.  M.  lies,  Am.  Jr.  Sc.,  May,  1882. 
Isometric;  occurs  in  octahedrons,  cubes  and  their  modifications;  also 
massive  and  in  imitative  shapes.  Color  tin-white,  inclining  to  steel-gray 
when  massive,  sometimes  iridescent.  Lustre  metallic.  H.  5'5-6.  G'  6'4 
to  7*2.  Analysis  of  Colorado  mineral  by  lies  :  cobalt  1T59,  iron  11*99, 
arsenic  63*82,  with  traces  of  lead,  bismuth  and  sulphur. 

Abundant  in  veins  near  Gothic,  Gunnison  County,  associ- 
ated with  erythrite,  native  silver,  pyrite  and  calcite.  Pro- 
duces erythrite  by  alteration. 

A1,ASKAITE.  (new).    Sulphide  of  Bismuth,   Lead  and  Silver.      G.  A. 

Konig,  Am.  Phil.  Soc.  Phil.,  1881. 

Massive,  small  foliated,  with  occasional  cleavage  planes.  Color  whitish 
lead-gray.  Lustre  metallic.  Easily  pulverized.  G.  6'878.  Cornp.,  sul- 
phur 17'63,  bismuth  56'97,  lead  1179,  silver  8.74,  copper  3'46,  antimony 
0'62,  zinc  079. 

Occurs  intimately  mixed  with  quartz,  barite,  chalcopyrite 
and  tetrahedrite  at  the  Alaska  mine,  Poughkeepsie  Gulch. 
San  Juan  county.  Named  after  the  Alaska  mine. 

BEBGERITE.  (new.)     Sulphide  of  Lead,  Copper  and  Bismuth.     G.  A.  Ko- 

nig, Am.  Chem.  Jr.,  1881. 

Isometric  ;  in  elongated  crystals  ;  also  massive.  Cubic  cleavage.  Color 
light  te  dark  gray.  Lustre  brilliant  metallic.  Comp.,  sulphur  14'97,  bis- 
muth 20*59,  lead  64'23,  copper  170. 

From  the  Baltic  lode,  near  Grant,  Park  county.  Named 
after  Mr.  Herman  Beeger,  of  Denver. 


Arsenical  Sulphide  of  Copper  and  Iron. 
Isometric  ;   usually  occurs  in  rhombic  dodecahedrons,  sometimes  variously 
modified  ;    also  jn  cubes  and  octahedrons,  of  which  the  edges  and  angles 
are  replaced.     Color  lead-gray  to  iron-black.     Lustre  metallic.     H.  3'5-4, 
G.  4'37.     Comp.,  varies,  copper  48,  sulphur  30,  arsenic  13,  iron  10. 

Occurs  in  the  Freeland  mine,  Clear  Creek  county,  in  clus- 
ters of  splendent  crystals  from  J  to  J  an  inch  in  diameter. 
A  few  dodecahedrons  are  met  with,  but  most  of  the  crystals 
appear  complicated.  Fine  specimens  in  collection  ot  com- 
piler. This  is  the  first  known  occurrence  of  the  mineral  in 
the  United  States. 


Antimonial   Sulphide  of  Lead.     W.  F.  Hillebrand,  Proc. 
Col.  Sci.  Soc.,  vol.  1. 

Orthorhombic  ;  crystals  regular  six-sided  prisms  terminated  by  low  six- 
sided  pyramids;  faces  of  prisms  generally  deeply  striated  longitudinally  ; 
also  massive,  fibrous  and  columnar.  Resembles  stibnite,  but  is  harder  and 
heavier.  Color  steel-gray.  Lustre  metallic.  H.  3-3'o.  G.  5'30-5.35. 
Analysis  of  Red  Mountain  mineral  by  Hillebrand  :  antimony  35*00,  arse- 
nic 5'64,  lead  3277,  copper  T22,  silver  0'23,  sulphur  22'50,  and  small 
amounts  of  iron,  soda,  etc. 

Occurs  massive  with  apparent  crystalline  structure,  of  iron- 
gray  color,  in  the  Brobdignag  mine,  Red  Mountain,  San  Juan 
county.  This  is  the  first  observed  occurrence  of  the  mineral 
in  the  United  States. 


Minerals  of  Colorado.  9 


Copper  Pyrites.    Sulphuret  of  Copper  and  Iron. 
Tetragonal  ;    the  crystals  present  the  general  form  of  the  tetrahedron  but 
are  sometimes  compound  ;    usually  occurs  massive  and  frequently  amor- 
phous.    Color  brass-yello\r,  often  with  a  variegated  taruish,    Lustre  me- 
tallic.    H.  3-5-4.     G.  415.     Comp.,  sulphur  34'9,  copper  34*6,  iron  30'5. 

Massive,  in  greater  or  less  quantity,  in  nearly  all  mines  in 
the  state,  and  nearly  always  highly  auriferous  when  found  in 
gold  mines,  and  argentiferous  when  found  in  silver  mines. 
That  from  the  mines  of  Red  Elephant  Mountain,  Clear  Creek 
county,  usually  carries  several  hundred  ounces  of  silver  in 
a  ton  of  ore.  Fine  tetrahedrons,  measuring  from  J  to  J  an 
inch  are  found  in  the  Freeland  mine,  Clear  Creek  county,  but 
nearly  all  are  incrusted  with  minute  crystals  of  tennantite. 
Fine  specimens  in  collection  of  J.  S.  Randall. 

BISMUXHIXITE.     Bismuth  Glance.     Sulphide  of  Bismuth. 

Orthorhombic  ;  occcurs  in  acicular  prisms,  striated  longitudinally  ;  also 
massive  with  a  foliated  or  fibrous  structure.  Color  lead-gray  inclining  to 
tin-white,  with  a  yellowish  or  iridescent  tarnish.  Lustre  metallic.  H.  2. 
G.  6-4-716.  Comp.,  sulphur  18'75,  bismuth  81'25. 

In  working  a  quartz  vein  near  Guy  Hill,  Jefferson  county, 
a  single  "pocket"  of  bismuthinite  was  encountered,  and  sev- 
eral hundred  pounds  of  the  ore  taken  out.  Occurs  in  stout 
columnar  aggregations  in  the  Las  Animas  mine,  near  Gold 
Hill,  Boulder  county.  In  quartz  veins  on  Big  Thompson 
Creek,  Larimer  county.  In  small  crystals  and  masses,  with 
a  gold-yellow  tarnish,  in  the  Little  Giant  lode,  Clear  Creek 
county.  Beautiful  specimens  in  collection  of  compiler. 


Arsenide  of  Iron.     W.  F.  Hillebrand,  Am.  Jr.  Sc.,  May, 
1884  ;  Proc.  Col.  Sc.  Soc.,  vol.  I. 

Orthorhombic;  occurs  in  right  rhombic  prisms,  parallel  to  whose  planes  it 
may  be  cleaved  ;  also  massive,  acicular  and  columnar.  H.  5-5"5.  G.  6*2, 
7'43.  Color  tin-white.  Lustre  metallic.  Analysis  of  Colorado  mineral 
by  Hillebrand  :  arsenic  71'  18,  iron  22'96,  cobalt  4'37,  sulphur  0'56,  bis- 
muth 0'08,  copper  0'39,  nickel  0'21. 

In  the  mines  on  Teocalli  and  White  Rock  Mountains,  in 
Gunnison  county,  in  dense  radiate  masses,  and  more  rarely  in 
trillings  and  minute  crystals,  associated  with  smaltite,  mar- 
casite,  galena,  chalcopyrite,  pyrargyrite,  argentite,  proustite 
and  native  silver,  in  a  gangue  of  calcite,  siderite  and  barite. 
Specimens  in  collection  of  Colorado  Scientific  Society. 


(new}.    Arsenical  Sulphide  of  Lead.     W.  F.  Hille- 
brand,  Proc.  Col.  Sc.  Soc.,  vol.  1. 

Occurs  massive  of  a  bluish-gray  color  and  slight  metallic  lustre.  H.  3. 
G.  5-94.  Analysis  by  Hillebrand  :  arsenic  13'00,  sulphur  19'56,  lead  61'63. 
copper  0'17,  silver  0'02,  iron  0'88,  oxygen  0'55. 

Occurs  massive  in  the  Zuni  mine,  near  Silverton,  and  forms 
the  matrix  of  zunyite.  Named  after  Franklin  Guiterman, 
who  first  brought  the  mineral  to  notice. 


10  Minerals  of  Colorado. 

R.HODOCHR.OSIXK.     Carbonate  ef  Manganese. 

Rhombohedral ;  occurs  in  saddle-shaped  lenticular  crystals ;  also  botry- 
oidal  and  massive.  H.  3'5-4'5.  G.  3'4-3'7.  Listre  vitreous  inclining  to 
pearly.  Color  shades  of  rose-red,  dark  red,  brown,  gray.  Translucent. 
Structure  lamellar.  Cornp.,  carbonic  acid  38'6,  protoxyd  of  manganese  61'4. 

In  beautiful  rose-red  translucent  single  crystals  in  the 
Royal  Albert  and  Mountain  Monarch  veins,  Uncompahgre 
district,  Ouray  county.  In  large  opaque  clusters  in  the 
Champion  vein,  Burrough's  Park,  Hinsdale  county  (Cross). 
In  small  white  radiate  bunches  upon  blue  celestite,  in  the 
Garden  of  the  Gods  (Hillebrand).  Some  fine  clusters  of 
crystals  have  been  found  in  the  Danube  mine,  near  Idaho 
Springs,  Clear  Creek  county.  Specimens  in  collection  of  J. 
S.  Randall. 

BR.OCHANTI'TK.     Hydrous  Sulphate  of  Copper.     Richard  Pearce,  Proc. 

Col,  Sc.  Soc.,  vol.  1. 

Orthorhombic ;  Occurs  in  well-defined  tabular  and  acicular  crystals  and 
drusy  crusts;  crystals  vertically  striated;  also  massive,  and  reniform 
with  a  columnar  structure.  H.  3'5-4.  G.  3'78.  Color  emerald-green  to 
blackish-green.  Lustre  vitreous.  Transparent,  translucent.  Comp.,  sul- 
phuric acid  19'9,  protoxide  of  copper  69,  water  ll'l. 

Occurs  in  considerable  quantity  and  very  pure,  with  par- 
tial development  of  crystal  form,  in  the  Monarch  mine,  Chaf- 
fee  county. 

FLrUORITE*     Fluor  Spar.     Fluorid  of  Calcium. 

Isometric  ;  occurs  in  cubes,  octahedrons,  rhombic  dodecahedrons  and  their 
modifications ;  crystals  often  have  their  faces  made  up  of  small  cubes,  or 
cavernous  with  rectangular  cavities ;  also  massiye,  coarse  or  fine  granular. 
Easily  cleaved  into  the  tetrahedron,  acute  rhombohedron  and  octahedron. 
H.  4.  G.  3'l-3'25.  Color  white,  grey,  and  various  tints  of  blue,  green, 
yellow,  purple  and  red.  Transparent  to  opaque.  Lustre  vitreous,  some- 
times splendent.  Fragments  heated  or  rubbed  against  each  other  in  the 
dark  become  luminous.  Comp.,  fluorine  48'7,  calcium  51'3. 

Large  veins  of  quite  pure  purple  fluorite  have  been  found 
on  St.  Vrains  Creek  and  Jim  Creek,  Boulder  county,  but  are 
undeveloped,  there  being  no  demand  for  it  at  present.  On 
Bear  and  Cub  Creeks,  Jefferson  county,  associated  with  ga- 
lena. Clusters  of  transparent  crystals,  of  green  color,  are 
found  on  Plum  Creek,  Douglas  county.  Some  very  good 
crystallized  specimens  are  found  in  the  Crystal  Mountains, 
El  Paso  county,  associated  with  amazonstone,  gothite,  etc. 
Massive  and  crystallized  of  a  deep  purple  color  on  Tarryall 
Creek,  South  Park.  It  also  occurs  sparingly  in  many  of 
the  mines  throughout  the  state.  Fluor  spar  is  used  as  a  flux 
in  the  reduction  of  ores,  and  is  the  source  of  hydrofluoric 
acid  for  etching  glass.  In  England  it  is  wrought  into  vases 
and  other  articles  for  ornament.  Specimens  in  collection  of 
J.  S.  Randall. 


Minerals  of  Colorado.  11 

CR.YO  WTB.     Fluoride  of  Sodium  and  Aluminum.      Cross  and  Hittebrand, 

Am.  Jr.  Sc.,  Oct.,  1883. 

Orthorhombic  ;  crystals  resemble  the  cube  ;  usually  occurs  massive  with  a 
rectangular  cleavage.  Color  usually  snow-white,  sometimes  brown  or 
black;  lustre  vitreous;  translucent  but  becomes  more  transparent  when 
immersed  in  water.  Melts  in  the  flame  of  a  candle.  H.  2*5.  G.  3.  Anal- 
ysis of  Colorado  mineral  by  Plillebrand:  Fluorine  53*55,  sodium  32*40, 
aluminum  12*90,  iron  oxide,  calcium  and  water. 

In  small  masses  in  quartz  and  feldspar  veins,  with  astroph- 
yllite,  zircon  and  columbite,  near  the  toll  road  at  St.  Peter's 
Dome,  west  of  Cheyenne  Mountain,  El  Paso  county.  Spec- 
imens of  the  cryolite  groupe  of  minerals  —  cryolite,  pachno- 
lito,  prosopite,  thomsenolite  and  gearksutite  —  in  collection  of 
Colorado  Scientific  Society.  Specimens  of  cryolite  in  collec- 
tion of  J.  S.  Randall.  Cryolite  is  used  for  making  soda  and 
soda  and  alumina  salts,  and  white  glass.  Produces  pachno- 
lite  on  alteration. 


Fluoride  of  Aluminum,  Calcium  and  Sodium.    Cross  and 
Hillebrand,  Am.  Jr.  Sc.,  Oct.,  1883. 

Monoclinic  ;  crystals  usually  four-sided  prisms  ;  also  occurs  massive.  Col- 
orless to  white  or  yellowish.  Transparent  to  translucent.  Analysis  by 
Hillebrand  of  Colorado  mineral  :  aluminum  12*36,  calcium  18*04,  sodium 
10*25,  water  8*05,  fluorine  51*30. 

Massive  and  in  small  transparent  crystals,  at  St.  Peter's 
Dome,  El  Paso  county.  Product  of  the  alteration  of  cryo- 
lite. Specimens  in  collection  of  compiler. 


Fluoride  of  Aluminum  and  Calcium.    Cross  and  Hillebrand, 
Am.  Jr.  Sc.,  Oct.,  1883. 

Moncclinic;  occurs  in  minute  imbedded  crystals.  Colorless,  white  or 
grayish.  H.  4*5.  G.  2*89.  Analysis  of  Colorado  mineral  by  Hillebrand, 
fluorine  35*01,  aluminum  23*37,  calcium  16*19,  magnesium  0*11,  sodium 
0*33,  water  12*41,  loss  as  oxygen  12*58. 

At  St.  Peter's  Dome,  massive  and  in  small  crystals,  with 
other  fluorides. 


Fluoride   of  Aluminum,   Calcium   and    Sodium. 
Cross  and  Hillebrand,  Am.  Jr,  Sc.,  Oct.,  1883. 

Monoclinic  ;  occurs  in  slender  prisms,  horizontally  striated  ;  also  massive, 
opal  or  chalcedony-like.  Color  white,  sometimes  reddish.  Lustre  vit- 
reous to  waxy.  Transparent  to  translucent.  H.  2*5-4.  G.  2*75.  Comp., 
fluorine  52*2,  aluminum  15*0,  calcium  15*4,  sodium  7*6,  water  9*8. 

Found  sparingly,   mixed  with   pachnolite,  at  St.    Peter's 
Dome. 

GBARKSUTIXE.     Fluoride  of  Aluminum,  Calcium  and  Sodium.     Cross 

and  Hillebrand,  Am.  Jr.  Sc.,  Oct.,  1884. 

Occurs  in  minute  needles  and  kaolin-like.  Color  white.  Lustre  dull. 
H.  2.  Analysis  of  Colorado  mineral  by  Hillebrand  :  aluminum  15*31, 
calcium  22*30,  fluorine  42*07,  water  15*46,  sodium  0*10,  potassa  0*04. 

Occurs  quite  abundant  as  minute  crystals  and  kaolin-like, 
at  St.  Peter's  Dome. 


12  Minerals  of  Colorado. 

ORTHOCLtASB.     Potash  Feldspar. 

Monoclinic  ;  occurs  in  modified  oblique  rhombic  prisms  ;  usually  thick 
often  rectangular,  and  also  in  modified  tables  ;  also  massive,  some- 
times lamellar.  Color  white,  gray  and  flesh-red  common  ;  also  greenish 
and  bluish,  when  it  is  called  Amazonstone.  Lustre  vitreous,  sometimes 
pearly  on  a  cleavage  face.  Cleaves  easily  into  plates,  Transparent  to 
subtranslucent.  H.  6.  G.  2'39-2'62.  Corap.,  silica  64'20,  alumina  18'40, 
potash  16'95. 

The  common  feldspar  of  granitic  rocks.  Fine  crystals 
are  abundant  in  the  Lida  the  Little  Queen  lode  at  Kokomo. 
Specimens  in  collection  of  J.  S.  Kandall. 

MICR.OCL*INK.     Feldspar.     Variety  Orthoclase. 

Color  pink  and  gray.      Composition,  etc.,  same  as  orthoclase. 

Associated  with  amazonstone,  etc.,  near  Florissant,  and 
occurring  in  the  same  crystalline  forms. 


Green  Feldspar.     Variety  Microcline. 
Crystallizes  in  the  same  system,  and  has  nearly  the  same   composition  as 
orthoclase.     Color  bluish-green.     According  to  Konig,  the  the  color  is  due 
to  iron. 

Fine  specimens  near  Florissant,  El  Paso  county,  in  cavities 
in  granite,  associated  with  smoky  quartz,  albite,  topaz,  phe- 
nacite,  fluorite,  gothite  and  columbite.  The  crystals  are  often 
of  great  size  and  frequently  in  groups.  Baveno  and  Carls- 
bad twin  crystals  are  quite  frequent.  Fine  specimens  in 
the  compiler's  cabinet. 

AI«BrrE.     Soda  Feldspar. 

Triclinic  ;  occurs  generally  in  flat  twin  crystals,  which  are  often  re- 
versed, the  one  upon  the  other;  also  massive,  either  lamellar  or  granular, 
the  laminae  sometimes  divergent  ;  granular  varieties  often  quite  fine.  Color 
varies  from  milk-white  to  green  or  red.  Lustre  pearly  upon  a  cleavage 
face.  Transparent  to  opaque.  H.  6-7.  G.  2'59.  Comp.,  silica  68'6,  soda 
11-8,  alumina  19'6. 

Near  Florissant  with  amazonstone,  sometimes  capping  crys- 
tals of  that  mineral,  but  more  frequently  forming  the  base  or 
matrix  in  which  the  crystals  are  set.  Often  in  granite  rocks. 

PIXCMSTONE.     Volcanic  Glass.     A  fused  feldspar. 

Occurs  massive.  Color  tints  of  green,  yellow,  red,  brown  and  black.  Lus- 
tre pitch-like  or  glassy.  Translucent  to  opaque.  Breaks  with  a  sharp 
edge.  H.  5-6.  Comp.,  either  orthoclase,  albite  or  oligoclase. 

Forms  a  dyke  on  the  north  wall  of  the  Colorado  Central 
mine,  Georgetown.  Found  near  Del  Norte. 

ZUNYIXE.  (new.)     Silicate  of  Alumina.     W.  F.  Hillebrand,  Proc.  Col.  Sci. 
Soc.,  vol.  1. 

Isometric;  occurs  in  tetrahedral  prisms  with  similar  terminations.  Col- 
orless when  pure,  but  often  black  from  impurities.  Lustre  vitreous. 
Transparent  to  opaque.  H.  7.  G.  2'87.  Analysis  by  Hillebrand  :  silica 
silica  24'33,  alumina  57'88,  lithia  10'89,  fluorine  5'61,  chlorine  2'91,  with 
traces  of  iron,  soda,  etc. 

Occurs  in  very  small  crystals  imbedded  in  guitermanite 
from  the  Zuni  mine  near  Silverton.  JSIamed  after  that  mine. 


Minerals  of  Colorado.  13 

COSAWTK.    Sulphide  of  Lead  and  Bismuth.     W.  F.  Hillebrand,  Am.  Jr., 

Sc.,  May,  1884;  Proc.  Col.  Sc.  Soc.,  vol.  1. 

Crystal  apparently  rhombic,  longitudinally  striated.  Color  lead-gray, 
grayish-white,  pale  yellow  on  exposed  surface.  Lustre  metallic.  H.  3'5. 
Analysii  ot  mineral  from  Comstock  mine,  by  Hillebrand  :  bismuth  42'93. 
lead  22;49,  sulphur  17  '11,  silver  8'43,  copper  7  '50. 

Occurs  in  irregular  masses,  rarely  an  inch  in  length,  with- 
out crystalline  structure,  in  the  Comstock  mine,  near  Parrott 
City,  La  Plata  county,  associated  with  pyrite,  sphalerite,  a 
telluride  and  gold  in  a  quartz  vein.  Massive  in  the  Yankee 
Girl  mine,  San  Juan  county.  Specimens  in  collection  of  Col- 
orado Scientific  Society, 

AUTUNITE*     Lime-Uranite.    Phosphate  of  Uranium  and  Lime. 

Orthorhombic  ;  crystals  very  nearly  square  and  cleavable.  Color  citron- 
to  sulphur-yellow.  Streak  yellowish.  Translucent.  Lustre  pearly  to  ad- 
amantine. H.  2-2-5.  G.  3-05-3-19.  Comp.,  phosphoric  acid  15*7,  oxyd 
of  uranium  62'7,  lime  6'17  water  15'5. 

Found  in  the  Peabody  lode,  near  Georgetown,  in  minute 
greenish-yellow,  tabular  crystals.  Also  in  a  lode  on  Chicago 
Creek,  Clear  Creek  county.  « 


Arsenical  Sulphide  of  Copper.    B.  S.  Burton,  Am.  Jr.  Sc., 
Jan.,  1868. 

Orthorhombic.  Massive,  granular  or  columnar.  Cleavage  perfect  giving 
a  brilliant  metallic  luster.  Color  grayish  to  iron-black.  Streak  grayish- 
black,  powder  having  a  metallic  luster.  Brittle.  H.  3.  G.  4"43.  Anal- 
ysis of  Willis  Gulch  mineral  by  Burton  :  sulphur  31'56,  copper  47'58, 
arsenic  17"80,  antimony  1"37,  iron  1*04. 

Occurs  massive  and  crystallized  in  the  Powers  lode,  Willis 
Gulch,  Gilpin  county.  Specimens  in  the  compiler's  collection. 

ACAXXHI'TE.     Silver  Glance  under  an  Orthorhombic  form. 

Orthorhombic  ;  crystals  usually  slender-pointed  prisms.  Luster  metallic. 
Color  iron-black.  Sectile,  cutting  like  lead.  Fracture  uneven,  giving 
a  shining  surface.  H.  2'5  or  under.  G.  7'16-7'33.  Comp.,  sulphur  12'9, 
silver  87  '1. 

Occurs  in  small  crystals  in  the  Little  Emma  mine,  George- 
town. Specimens  in  compiler's  collection. 

AR.OBKXITE.     Silver  Glance.    Vitreous  Silver.    Sulphuret  of  Silver. 

Isometric  ;  primary  form  the  cube  ;  also  occurs  in  octahedrons  and  rhom- 
bic dodecahedrons;  reticulated,  dendritic,  stalactitic,  amorphous  and 
massive.  Color  blackish  lead-gray.  Streak  shining.  Luster  metallic. 
Fracture  small  sub-conchoidal,  uneven.  Perfectly  sectile,  cutting  like 
lead.  H.  2-2*5.  G.  7'196-7'365.  Comp.,  sulphur  12'9,  silver  87;L 

This  valuable  ore  of  silver  occurs  in  small  quantities  in 
nearly  all  the  silver  mines  in  the  state,  but  is  seldom  found  in 
masses  weighing  more  than  two  or  three  pounds,  although 
frequently  found  in  sufficient  quantities  to  make  the  ore  with 
which  it  is  associated  a  high  grade  silver  ore.  Very  good 
crystallized  specimens  are  occasionally  met  with  in  the 
Georgetown  mines.  Specimens  in  compiler's  collection. 


14  Minerals  of  Colorado. 


BI^ACK.    Sulphuret  of  silver  in  the  form  of  a  powder  or  stain. 
Of  frequent  occurrence   at   the   surface   of  silver-bearing 
veins.     Commonly  called  "sulphurets." 

CHALCEDONY.     Cryptocrystalline  variety  of  Quartz. 

Occurs  in  matnmillated,  botryoidal  and  stalactitic  forms,  but  never  in  a 
crystallized  state.  Luster  like  that  of  wax.  Color  white,  grayish,  pale- 
brown  to  dark-brown  and  black,  rarely  delicate  blue.  H.  7.  G.  2'5-2'8. 
Cornp.,  silica,  with  some  opal  silica. 

Abundant  on  the  ridge  to  the  left  of  Willow  Creek  in  Mid- 
dle Park  ;  also  in  the  basalt  on  Corral  Creek.  Handsome 
pale  blue  specimens  near  the  Salt  Works  in  South  Park;  six 
miles  south  of  the  Salt  Works  in  jasper  and  semi-opal.  Fine 
specimens  in  San  Luis  Park  on  La  Garita,  filling  cavities  of 
amygdaloid.  At  Los  Pinos  Agency,  in  basalt.  At  the  head 
of  Cherry  Creek,  pseudomorphous  after  wood.  On  the  Rio 
Grande,  15  miles  above  Loma,  large  geodes.  Blue  specimens 
on  the  Gunnison  above  the  Grand  Canon.  Common  in  the 
valley  of  the  Gunnison  near  Grand  River.  Fine  specimens  in 
the  compiler's  collection.  > 


Erubescite.  Purple  Copper  Ore. 
Isometric  ;  the  crystals  are  generally  cubes  of  which  the  solid  angles  are 
replaced,  and  the  faces  are  mostly  curvilinear.  Usually  massive.  Color 
between  copper-red  and  pinchbeck  -brown,  but  it  soon  acquires  an  irides- 
cent tarnish.  Streak  pale  grayish-black.  Luster  metallic.  Brittle.  H. 
3.  G.  4-4-5-5.  Comp.,  varies,  sulphur  22'11,  copper  70'13,  iron  7'76. 

A  valuable  gold-ore  in  the  gold  mines,  and  in  some  mines 
is  quite  abundant.  Frequently  found  in  silver-bearing  veins, 
and  sometimes  becomes  a  valuable  ore  of  silver.  In  the  com- 
piler's collection  are  some  very  good  crystals  from  Central. 


Cross  &  Hillebrand,  Am.  Jr.  Sc.,  June,  1882  ;    Bulletin  No. 
20,  U.  8.  Geo.  Sur. 

Rhombohedral  ;  usually  occurs  crystallized  in  obtuse  rhombohedrons,  and 
has  a  rhombohedral  cleavage.  Color  white  and  reddish.  Luster  vitre- 
ous. Transparent  to  translucent.  H.  4-5.  G.  2'08-2'19.  Analysis  of 
Golden  mineral  by  Hillebrand  :  silica  47'18,  alumina  19'67,  potash  0'37, 
lime  9-74,  strontia  9'43,  soda  (V51,  water  25'15. 

Good  glassy-white  specimens  are  quite  abundant  in  the 
amygdaloid  of  North  Table  Mountain,  Golden.  Specimens 
of  all  the  Table  Mountain  minerals  in  the  compiler's  cabinet. 

SXIUBITK.     Radiated  Zeolite.     Bulletin  No.  20,  U.  S.  Geo.  Sur. 

Orthorhombic  ;  usually  occurs  in  prisms  of  which  the  edges  are  replaced, 
and  with  four-sided  summits  ;  often  in  sheaf-like  aggregations  and  in  di- 
verging groups  ;  also  massive,  in  radiating  and  broad  columnar  forms. 
Color  white,  sometimes  yellow,  gray,  red  or  brown.  Transparent  to  trans- 
lucent. Luster  vitreous.  Double  refracting.  H.  3'5-4.  G.  2'094r-2'161. 
Analysis  of  Golden  mineral  by  Hillebrand  :  silica  54'67,  alumina  16*78, 
lime  7-98,  soda  T47,  water  19'16. 

Occurs  sparingly  in  small,  clear  crystals  in  the  amygdaloid 
of  Forth  Table  Mountain,  Golden. 


Minerals  of  Colorado.  15 

I^AUMONTIXK.     Cross  and  Hillebrand,  Am.  Jr.  Sc.,  Aug.,  1882,   U.  £ 

Geo.  Sur.,  Bui.  20. 

Monpclinic ;  occurs  in  columnar,  radiating  and  compact  crystalline  masses, 
and  in  separate  crystals.  Color  white  or  yellowish-white,  sometimes  red- 
dish. Luster  vitreous  to  earthy.  Transparent  to  opaque;  becoming 
opaque  and  sometimes  pulverulent  on  exposure.  H.  3*5-4.  G.  2*25-2*36. 
Analysis  of  Table  Mountain  mineral  by  Hillebrand  :  silica  52*07,  alumina 
21*30,  lime  H'24,  potassa  0*42,  soda  0*48,  water  14*58. 

Occurs  as  a  reddish-yellow  sand-like  material,  and  in  com- 
pact crystalline  masses  in  the  cavities  of  the  amygdaloid  of 
North  Table  Mountain  at  Golden. 

THOMSONITE.         Cross  and  Hillebrand,  Am.  Jr.  Sc.,  June,  1882;  Bulle- 
tin No.  20,  U.  S.  Geo.  Sur. 

Orlhorhombic ;  occurs  in  right  rectangular  prisms,  with  cleavage  parallel 
to  its  side ;  usually  massive  with  a  columnar  or  radiated  structure ;  also  in 
radiated  spherical  concretions.  Luster  vitreous  inclining  to  pearly.  Color- 
less or  snow-white  ;  impure  varieties  brown.  Transparent  to  translucent. 
Pyroelectric.  H.  5-5*5.  G.  2*3-2*4.  Analysis  of  Golden  mineral  by  Hil- 
lebrand :  silica  42*66,  alumina  29*25.  lime  10*90,  soda  4*92,  water  12*28. 

Occurs  in  the  amygdaloid  of  Table  Mountains,  Golden,  in 
minute  rectangular  blades,  which  are  placed  upon  each  other 
like  the  leaves  of  a  closed  fan,  and  in  spherical  concretions 
having  a  radiated  structure. 

ANAI.CITE.     Cross  and  Hillebrand,  Am.  Jr.  Sc.,  June,  1882 ;    Bulletin  No. 

20,  U.  S.  Geo.  Sur. 

Isometric ;  usually  occurs  in  trapezohedrons,  or  24-sided  crystals ;  also 
massive.  Luster  vitreous.  Transparent  to  opaque.  Colorless,  white,  oc- 
casionally grayish,  greenish,  yellowish  or  reddish-white.  H.  5-5*5.  G. 
2*22-2*29.  Analysis  of  Gold'en  mineral  by  Hillebrand:  silica  55*80, 
alumina  22*45,  soda  13*45,  water  8*35. 

Occurs  in  pure  white  or  transparent  crystals,  and  vary  in 
size  from  small  ones  to  those  nearly  an  inch  in  diameter,  in 
the  amygdaloid  of  North  Table  Mountain,  Golden.  On  the 
eastern  side  of  the  mountain,  analcite  is  specially  abundant. 
It  is  also  abundant  on  South  Table  Mountain,  but  the  crys- 
tals are  usually  quite  small. 

APOPHYU/TB.     Ooss  and  Hillebrand,  Am.  Jr.  Sc.,  August,  1882 ;  Bul- 
letin No.  20,  U.  S.  Geo.  Sur. 

Tetragonal ;  occurs  in  right  square  prisms  or  octahedrons,  which  often 
terminate  in  a  sharp  pyrimid  ;  crystals  sometimes  nearly  cylindrical  or 
barrel-shaped;  also  massive  and  lamellar.  Cleavage  highly  perfect  to 
all  the  planes  of  the  primary  form.  Color  white  or  grayish,  sometimes 
greenish,  yellowish,  or  reddish.  Luster  vitreous  to  pearly.  Transparent 
to  opaque.  H.  4*5-5.  G.  2*3-2*4.  Analysis  of  Golden  mineral  by  Hille- 
brand: silica  51*89,  alumina  1*54,  iron  0*13,  lime  24*51,  potash  3*81,  soda 
0*59,  water  16*52,  fluorine  1*70. 

Occurs  in  well-developed  crystals  of  prismatic  habit  in  the 
amygdaloid  of  North  Table  Mountain,  Golden.  The  larger 
crystals  which  are  occasionally  half  an  inch  in  diameter,  are 
often  of  a  greenish  tinge,  and  have  uneven  surfaces  and  are 
terminated  by  a  large  number  of  small  pyramids. 


16  Minerals  of  Colorado. 

A  pearly-white,  very  finely-foliate  substance  resembling 
albin  is  produced  by  the  alteration  of  apophyllite,  which  ac- 
cording to  Hillebrand,  consists  of  silica  67'96,  alumina  8-48, 
iron  oxyd  1-04,  lime  5'47,  magnesia  0-53,  potassa  1-23,  soda 
0*74,  water  14-55. 


Fibrous  Zeolite.     ~0ross  and  Hillebrand,  Am.  Jr.  Sc.,  August, 
1882  ;  Bulletin  No.  20,  U.&  Qeo.  Sur. 

Occurs  in  long  slender  crystals,  often  very  delicate  ;  also  in  silky  fibrous  or 
columnar  masses.  Luster  of  crystals  vitreous  ;  of  fibrous  masses  more  or 
less  silky.  Colorless  or  white,  grayish  or  yellowish.  Fragile.  Transpa- 
rent to  translucent.  H  .5.  G.  2'2-2'4.  Analysis  of  Golden  mineral  by  Hil- 
lebrand :  silica  46'17,  alumina  26'88,  lime  877,  soda  6'19,  water  12'16. 

Occurs  in  the  amygdaloid  of  North  Table  Mountain,  Gol- 
den, in  masses  composed  of  exceedingly  delicate  needles 
loosely  grouped  together,  and  sometimes  as  a  continuous 
membrane,  or  like  a  thick  cobweb. 

NATR.O  WTE.    Needle  Zeolite,     Cross  and  Hillebrand,  Bulletin  No.  20, 

U.  S.  Geo.  Sur. 

Orthorhombic  ;  crystals  usually  slender,  often  acicular  ;  frequently  inter- 
lacing, divergent,  or  stellate  ;  also  fibrous,  radiating,  massive,  granular,  or 
compact.  Luster  vitreous  to  pearly.  Transparent  to  translucent.  Color 
white  or  colorless,  yellowish,  grayish  or  reddish.  H.  5-5'5.  G.  2'17-2'25. 
Analysis  of  Table  Mountain  mineral  by  Hillebrand  :  silica  43'66,  alumina 
24-89,  lime  4'87,  soda  14'66,  water  8'09. 

Natrolite  is  the  least  abundant  of  the  zeolites,  and  has  been 
found  only  on  the  northern  part  of  South  Table  Mountain, 
where  it  appears  in  delicate  prisms  sparingly  deposited  upon 
analcite  or  associated  with  that  mineral.  It  has  also  been 
observed  upon  yellow  calcite,  chabazite  and  thomsonite. 


Cross  and  Hillebrand,  Bulletin  No.  20,  U.  S.  Geo.  Sur. 
Rhombohedral  ;  occurs  in  twin  crystals,  the  faces  of  which  are  often  stri- 
ated ;  frequently  in  druses.  Colorless,  white,  grayish,  greenish,  reddish, 
yellowish.  Luster  vitreous.  Transparent  to  translucent.  H.  4-4'5.  G. 
2'09-2'16.  Analysis  of  Golden  mineral  by  Hillebrand  :  silica  4676, 
alumina  21'91,  lime  H'12,  potassa  0'21,  soda  1'34,  water  18M35. 

Small  white  and  colorless  crystals  occur  sparingly  in  the 
amygdaloid  of  North  Table  Mountain,  Golden.  Associated 
with  the  levynite  is  a  fibrous  mineral,  dull  white  in  color  and 
never  showing  crystal  faces,  which  is  almost  identical  with 
the  levynite  in  composition. 


Fibrous  Zeolite.     Cross  and  Hillebrand,  Bulletin  No.  20,  U. 
8.  Geo.  Sur. 

Monoclinic;  occurs  in  long  or  short  prismatic  or  acicular  crystals  ;  very 
often  in  twins  ;  also  massive  with  a  fibrous  or  radiating  structure.  Color- 
less, snow-white,  grayish  yellowish,  and  reddish.  Transparent  to  translu- 
cent. Luster  vitreous,  or  silky  when  fibrous.  H.  5-5'5.  G.  2'16-2'40. 
Analysis  of  Golden  mineral  by  Hillebrand:  silica  46'03,  alumina  25*28, 
iron  oxyd  0'27,  lime  1277,  soda  1'07,  potassa  0'13,  water  14'48. 

Occurs  sparingly  in  small  cavities  in  a  zone  just  above  that 


Minerals  of  Colorado.  17 

containing  a  great  number  of  zeolites  on  North  Table  Moun- 
tain, Golden.  It  appears  in  small  spheres  or  segments  of 
spheres  with  a  radiate  structure,  and  resembles  thomsonite, 
though  easily  distinguished  by  the  brilliant  white  color  and 
satin-like  luster. 


Variety  of  Halloysite.  Hydrous  Silicate  of  Alumina.  Cross  and 
Hillebrand,  Bulletin  No.  20,  U.  S.  Geo.  Sur. 
Occurs  massive  ;  clay-like  or  earthy.  Luster  somewhat  pearly  or  waxy. 
Feels  greasy.  Colors  usually  dark.  H.  1-2.  G.  l'8-2'4.  Analysis  of 
Golden  mineral  by  Hillebrand  :  silica  4617,  alumina  22'03,  iron  oxyd 
4'64,  lime  2'30,  magnesia  2'42,  potassa  and  soda  2'06,  water  2O38. 

Occurs  in  the  amygdaloid  about  the  center  of  South  Table 
Mountain,  Golden,  as  a  dark  brown  clay.  Placed  in  water  it 
falls  apart  without  decrepitation,  unlike  ordinary  bole.  The 
mineral  is  used  as  a  pigment. 

HUBNER.IXK.     Tungstate  of  Manganese.     Cross  and  Hillebrand,  Bulletin 

No.  20,  U.  S.  Geo.  Sur.;  Proc.  Col.  Sc.  Soc.,  vol.  1. 

Orthorhombic;  usually  occurs  in  columnar  masses  or  foliated.  Luster  ad- 
amantine on  face  of  cleayage;  elsewhere  greasy.  Color  brownish-  red, 
brownish-black,  yellowish.  Streak  yellowish-brown.  Opaque.  H.  4'5. 
G.  7'4.  Analysis  ot  mineral  from  Koyal  Albert  vein  by  Hillebrand  :  silica 
0'62,  tungstic  acid  75'58,  protoxyd  of  manganese  23'40,  protoxyd  of  iron 
0-24,  lime  0'13,  columbic  acid  (?)  0'05. 

The  mineral  occurs  in  the  Royal  Albert  vein,  Uncompahgre 
district,  Ouray  county,  in  long  flattened  crystals  vertically 
striated,  of  a  brownish-black  to  pale  yellow  color,  imbedded 
in  quartz.  It  is  also  found  near  Silverton,  and  at  Jimtown, 
Boulder  county,  where  it  appears  in  small  blades  disseminated 
through  quartz.  Specimens  in  compiler's  cabinet. 

HEX1OXROPB.     Bloodstone.     Cryptocrystalline  Quartz. 

A  bright  to  leek-green  variety  of  chalcedony  or  jasper,  with  small  spots  of 
red  jasper  looking  like  drops  of  blood. 

Occurs  in  a  vein  of  jasper  in  the  hill  at  the  junction  of  Wil- 
low Creek  and  the  Grand  River,  Middle  Park.  On  account 
of  its  beautiful  color,  heliotrope  has  always  been  much  used 
for  rings,  seals  and  other  ornaments.  Specimens  of  the  diff- 
ferent  forms  of  quartz  in  the  compiler's  cabinet. 


Cryptocrystalline  Quartz. 
A  variety  of  chalcedony  (p.  14)  of  a  clear  bright  red  tint,  pale  to  deep  in 
shade.     The  brownish-red  is  also  called  carnelian.    The  color  is  due  to  the 
presence  of  iron. 

Found  sparingly  on  the  ridge  to  the  left  of  "Willow  Creek 
in  Middle  Park;  on  the  Rio  Grande  near  Loma;  near  Lark- 
spur; on  Cherry,  Kiowa  and  Running  Creeks,  pseudomorph- 
ous  after  wood.  From  the  high  polish  of  which  it  is  suscept- 
ible, and  its  bright  colors,  carnelian  has  always,  in  both  an- 
cient and  modern  times,  been  much  used  for  ornaments. 


18  Minerals  of  Colorado. 

PRASE*     Cryptocrystalline  Quartz. 

A  translucent  leek-green  chalcedony  (p.  14). 

Occasionally  found  in  San  Luis  Park. 

CHRYSOPRASE.     Cryptocrystalline  Quartz. 

An  apple-green  chalcedony  (p.  14),  the  color  of  which  is  due  to  the  pres- 
ence of  nickel. 

Occurs  sparingly  on  La  Garita,  west  of  San  Luis  Park.  In 
geodes  in  Middle  Park. 

BAIMDED  AGATE.  Fortification  Agate.  Eye  Agate.  Clouded  Agate. 
A  variegated  chalcedony.  The  colors  are  either  banded  or  in  clouds.  The 
bands  are  delicate  parallel  lines  of  various  shades  of  color.  They  follow 
waving  or  zigzag  courses,  and  are  occasionally  concentric  circular,  when  it 
it  is  called  eye  agate.  When  the  colors  are  irregular  it  is  called  clouded 
agate. 

Banded  and  clouded  agates  are  occasionally  found  on  Wil- 
low Creek  in  Middle  Park ;  near  the  Salt  Works  in  South 
Park;  near  the  source  of  Cherry  Creek ;  ten  miles  south  of 
Canon  City,  in  sandstone;  on  the  La  Garita,  south  of  San 
Luis  Park;  large  geodes  on  the  Rio  Grande,  15  miles  above 
Loma.  Owing  to  its  beauty,  variety,  hardness  and  capability 
of  receiving  a  high  polish,  agate  is  much  used  both  in  articles 
of  utility  and  ornament. 

MOSS   AGATE.     Mocha  Stone. 

A  chalcedony  filled  with  brown,  black,  green  or  red  moss-like  or  dendritic 
forms. 

Abundant  on  Williams  Fork,  Middle  Park;  in  South  Park 
between  Fairplay  and  the  Salt  Works. 

AGATIZEO  WOOD. 

Wood  petrified  with  clouded  agate. 

Middle  Park  near  Hot  Spring,  and  on  the  right  of  Willow 
Creek;  around  the  Salt  Works  in  South  Park;  abundant 
near  the  sources  of  Cherry,  Kiowa  and  Bijou  Creeks. 

OXYX. 

Like  agate  in  consisting  of  layers,  but  the  layers  are  in  even  planes  and 
usually  thicker.  The  colors  are  generally  of  a  light  brown  and  an  opaque 
white. 

Occurs  sparingly  on  the  ridge  to  the  left  of  Willow  Creek, 
in  Middle  Park, and  also  near  Grand  Lake;  on  the  La  Garita, 
west  of  San  Luis  Park;  a  variety  called  chalcedonyx is  found 
in  San  Luis  Park.  Eextensively  used  for  cameos  and  other 
articles  of  adornment. 

SARDOXYX. 

Those  varieties  of  onyx  which  are  composed  of  alternate  layers  of  red  and 
white. 

A  few  specimens  have  been  found  in  the  Willow  Creek 
region,  Middle  Park.  It  is  the  most  beautiful,  the  rarest  and 
most  valuable  form  of  onyx. 


Minerals  of  Colorado.  19 

PYRARGYIMXB.    Kuby  Silver.    Dark  Bed  Silver  Ore. 

Rhombohedral  ;  crystals  usually  prismatic  ;  generally  occurs  in  small 
masses.  Lustre  metallic-adamantine.  Color  black,  approaching  coch- 
ineal-red. Streak  cochineal-red.  Translucent-opaque.  H.  2-2*5.  G.  5'7, 
Comp.,  sulphur  177,  antimony  22'5,  silver  59'8. 

Occurs  in  small  masses  in  most  of  the  silver  mines  in  the 
state,  but  rarely  found  crystallized.  Specimens  in  compiler's 
collection. 

PR.OUST1XB.     Light  Kuby  Silver  Ore. 

Rhombohedral  ;  occurs  in  granular  masses  and  in  small  crystals.  Lustre 
adamantine.  Color  cochineal-red.  Streak  cochineal-red,  sometimes  in- 
clined to  aurora-red.  Subtransparent  —  subtranslucent.  H.  2.-2'5.  G. 
5'42-5'56.  Comp.,  sulphur  19'4,  arsenic  15'2,  silver  65'4. 

Occurs  in  the  mines  of  Geneva  District  and  about  Monte- 
zuma  in  small  masses  and  in  clusters  of  minute  crystals.  In 
the  Colorado  Central  mine,  Georgetown,  in  beautiful  crystals 
and  massive,  associated  with  galena,  sphalerite  and  crystals 
of  polybasite.  Compiler's  collection. 


Indigo  Copper  Ore. 
Hexagonal,  but  rarely  occurs  in  crystals  ;  commonly  massive  or  spheroidal. 
Color  indigo-blue  or  darker.     Streak  lead-gray  to  black,  shining.      Lustre 
of  crystals  submetallic  ;    dull  when  massive.     H.  l'5-2.     G.  4'59.     Comp., 
sulphur  33'5,  copper  66'5. 

Occurs  in  small  grains  in  the  Pewabic  lode,  Central  City. 
In  the  form  of  a  powder  in  some  of  the  mines  of  Cascade  and 
Daily  Districts,  Clear  Creek  County. 

COI^UMBIXB.     Columbate  of  Iron.     Ore  of  Columbium.    J.  L.  Smith, 

Am.  Jour.  Sc.,  May,  1877. 

Orthorhombic  ;  occurs  in  single  crystals,  crystalline  masses,  rarely  massive. 
Lustre  submetallic;  a  little  shining.  Color  iron-black,  brownish-black, 
grayish-black  ;  often  iridescent.  Streak  dark  red  to  black.  Fracture  sub- 
conchoidal,  uneven.  H.  6.  G.  5  4-6'5.  Analysis,  Colorado  mineral,  by 
J.  L.  Smith  :  columbic  acid  79'61,  iron  protoxide  14*14,  manganese  pro- 
toxide 4'61,  loss  by  heat  '50. 

In  the  Pike's  Peak  region,  in  small  black  acicular  crystals 
imbedded  in  amazonstone.  A  few  large  single  crystals  and 
fragments  have  been  also  been  found.  Compiler's  collection. 


Cross  and  HUlebrand,  Bui.  No.  20,  U.  S.  Geo.  Sur. 
Isometric;  in   cubes  and  octahedrons.     Colorless.     Transparent.     H.  4*5. 
G.  2'4.     Comp.,  alumina  22'94,  fluorine  5O05,  calcium  T99,  magnesia  5'52, 
sodium  4'66,  water  14'84, 

Occurs  in  minute  crystals  in  cavities  in  thomsenolite  and 
pachnolite,  at  St,  Peter's  Dome,  El  Paso  County.  The  crys- 
tals here  found  are  transparent  cubes  whose  corners  are'  re- 
placed by  small  octahedron  faces  and  seldom  reach  a  diam- 
eter of  1MM.  Some  crystals  of  pachnolite  seem  to  be  coated  by 
a  crystalline  dust  whose  particles  are  found  under  the  micro- 
scope to  be  most  perfect  little  crystals  of  ralstonite. 


20  Minerals  of  Colorado. 

BIvP  ASOMTBi  i  (new.)     Cross  awd  Hillebrand,  Bui  No.  20,  Z7.  &  Geo.  SJw* 

n  ^lm.  Jr.  Sc.,  October,  1883. 

Probably  ,  isometric  ;  crystals  faces  cube  and  octahedron.  Colorless,  but 
not  perfectly  clear.  Calculated  analysis  by  Hillebrand:  alumina  11'32, 
calcium  0'72,  magnesia  G'22^  potassium  28'94,  sodium  9'90,  fluorine  46'98. 

Sparingly  as  a  compact  irregular  mass  iu  cavities  in  mass- 
ive pachnolite  from  St,  Peter's  Dome,  El  Paso  County,  from 
which  it  was  named. 

ZIRCON.     Ooss  and  Hillebrand,  Am.  J.  Sc.,  Oct.,  1882  ;  Konig,  Am.  Phi.  Soc. 

xvi,  518,  1877. 

Tetragonal  ;  primary  form  an  obtuse  octahedron  with  a  square  base  ;  also 
occurs  in  irregular  forms  and  grains.  Lustre  adamantine.  Colorless,  pale 
yellowish,  grayish,  yellowish-green,  brownish-yellow,  reddish-brown. 
Transparent  to  ;  opaque.  Fracture  conchoidal  and  brilliant.  Double  re- 
fraction strong,  positive.  H.  7;5.  G.  4'5-4'75.  Comp.,  silica  33,  zirconia 
67.  Konig  made  an  analysis  of  zircon  from  the  Pike's  Peak  region,  which 
was  published  in  the  Proceedings  of  the  American  Philosophical  Society 
of  Philadelphia,  in,  1.877. 

Found  in  numerous  localities  in  the  Pike's  Peak  region, 
associated  with  astrophyllite,  amazon  stone,  etc.  Near  the 
Pike's  Peak  toll-road,  about  due  west  from  Cheyenne  Moun- 
tain, a  prospect  tunnel,  in  following  a  vein-like  mass  of  white 
quartz  in  granite,  disclosed  zircon  imbedded  in  the  quartz  so 
abundant  that  a  cubic  inch  of  the  latter  mineral  contains  from 
25  to  100  crystals  and  particles'  of  zircon,  varying  in  size  from 
I™  downward.  Some  of  these  crystals  are  very  perfect,  but 
exhibit  only  the  pyramid,  the  prisim  entirely  lacking.  Many 
of  them  are  beautifully  clear  and  of  deep  reddish-brown,  pink, 
pale  honey-yellow  and  occasionally  deep  emerald-green  color. 
The  perfection  of  these  crystals,  with  their  transparency  and 
color,  make  them  among  the  most  beautiful  known.  Small 
irregularly  shaped  zircons  and  occacionally  elongated  crystals 
occur  in  the  sands  of  Bear  Kiver.  They  are  of  various  shades 
of  brown,  red  and  yellow,  and  many  are  colorless.  Most  of 
them  are  transparent  and  qujte  brilliant,  but  too  small  to  be 
cut  for  setting.  Specimens  from  both  the  above  localities  in 
the  compiler's  cabinet.  Although  the  zircon  is  but  rarely 
used  in  jewelry,  it  makes  a  beautiful  gem  when  of  good  color 
and  has  a  peculiar  opalescent  reflection. 


Magnesia  Alum.      Goldsmith,  Proc.  Acad.  Nat.  Sci. 
1876. 

In  fine  acicular  crystals  ;  long  fibrous  masses  ;  and  efflorescences.  Lustre 
silky.  Color  white  or  yellowish.  Becomes  pulverulent  and  white  on  ex- 
posure. Taste  hitter  —  astringent.  H.  1.  Analysis  of  Monument  Park 
mineral  by  Goldsmith  :  sulphuric  acid  38'69,  alumina  1T90,  magnesia  4'89, 
potassa-and  soda  0'68,  sand  1'90,  water,  by  difference,  41'94. 

Occurs  crystallized  in  thin  needles  in  the  region  of  Monu- 
ment Park. 


Minerals  of  Colorado.  21 

AI^TAITE.    Telluride  of  Lead.     Genth,  Am.  Phi.  Soc.,  1874. 

Isometric;  usu?lly  massive;  rarely  in  cubes.  Cleavage  cubic.-  Lustre 
metallic.  Color  tin-white,  resembling  that  of  native  antimony,  with  a  yel- 
low tarnish,  Sectile.  H.  3-3'5.  G.  8'159.  Analysis  by  Genth  of  mineral 
from  the  Red  Cloud  mine,  Boulder  county:  quartz  0'19,  gold  O'l  9,  silver 
0'62,  copper  0'06,  lead  60'22,  zinc  9'15,  iron  0'48,  tellurium  37'99. 

Occurs  in  a  number  of  the  tellurium-bearing  mines  at  Gold 
Hill,  Boulder  County.  Fine  crystals  in  the  Slide  mine. 

CASSITERTXE.     Tin-Stone.     Oxyd  of  Tin.     Cross  and  Hillebrand,  Bui. 

20,  U.  S.  Geo.  Sur. 

Tetragonal  ;  primary  form  an  obtuse  pyramid  with  a  square  base  ;  it  is 
found  in  quadrangular  prisms,  terminated  by  four-sided  pyramids,  and  in 
many  more  complex  forms;  often  in  reniform  shapes.  Structure  fibrous 
divergent  ;  also  massive,  granular  or  impalpable.  Lustre  adamantine,  and 
crystals  usually  splendent.  Color  brown  or  black  ;  sometimes  red,  gray, 
white  or  yellow.  Streak  white,  grayish,  brownish.  Nearly  transparent  to 
opaque.  H.  6-7,  G.  6'4-7'l.  Comp.,  tin  78-67,  oxygen  21'33. 

Occurs  in  small  crystalline  masses  imbedded  in  albite  and 
quartz  on  Devil's  Head  Mountain,  Douglas  County,  associated 
with  topaz,  amazonstone,  smoky  quartz  and  fluor  spar. 
With  amazonstone  at  Florissant. 


Cerium-Epidote.  Iddings  and  Cross,  Am.  Jr.  Sc.,  Aug.,  1885. 
Monoclinic  ;  isomorphous  with  epidote  ;  crystals  either  short,  flat  tabular, 
or  long  and  slender,  sometimes  acicular  ;  twins  like  those  of  epidote  ;  also 
massive  and  in  angular  and  rounded  grains.  Lustre  submetallic,  pitchy 
or  resinous  —  occasionally  vitreous.  Color  pitch-brown  to  black,  either 
brownish,  greenish,  grayish  or  yellowish.  Streak  gray,  sometimes  slightly 
greenish  or  brownish.  Subtranslucent  to  opaque.  Fracture  uneven  or 
subconchoidal.  Double  refraction  either  distinct  or  wanting.  H.  5'5-6. 
G.  3'9-4'2.  Comp.,  silica  33,  alumina  15,  protoxide  of  iron  15,  cerium  21, 
lime  11,  lanthanium,  didymium,  yttria,  manganese,  etc. 

Forms  an  accessory  constituent  of  the  biotite  porphyrite  of 
Ten-Mile  District,  Summit  County,  in  which  the  crystals  oc- 
cur of  a  brilliant  black  color  and  oily  lustre.  In  the  porphy- 
rite of  Mount  Silverheels,  Park  County,  of  a  chestnut-brown 
color.  In  the  gneiss  of  the  Medicine  Bow  Range,  the  quartz 
porphyry  of  the  Mosquito  Range,  and  on  Eagle  River. 


Hydrous  Silicate  of  Alumina.     Konig,  Proc.  Acad.  Nat. 
Sci.  Phila.,  1876. 

Amorphous;  usually  in  thin  incrustations,  with  mammillary  surface; 
sometimes  stalactitic;  occasionally  almost  pulverulent.  Lustre  vitreous 
to  subresinous  ;  bright  and  waxy  internally.  Color  pale  sky-blue,  some- 
times greenish  to  deep  green,  brown,  yellow  or  colorless.  Streak  uncol- 
ored.  Translucent.  Fracture  imperfectly  conchoidal  and  shining  to 
earthy.  Very  brittle.  Adheres  to  the  tongue.  H.  3.  G.  1*85.  Comp., 
silica  22,  alumina  33,  water  41.  An  analysis  by  Genth  of  what  was  sup- 
posed to  be  chrysocolla,  from  Bergen  Park,  gave  33.85  alumina,  and  5'40 
of  copper  oxide,  which  corresponds  to  allophane  and  chrysocolla  in  the 
ratio  of  5:1. 

Forms  a  thin  bluish  crust  on  limonite  near  Bergen  ranch, 
Jefferson  County. 


22  Minerals  of  Colorado. 


Soda  Hornblende.  Konig,  Am.  Phi.  Soc.,  1877. 
Probably  ruonoclinic;  occurs  in  crystals  and  cleavable  masses.  Color 
pure  black;  in  thin  scales  deep  green  to  brown.  Streak  grayish-green. 
H.  6.  G.  3'44.  Comp.,  silica  50'5,  sesquioxyd  of  iron  26'9,  protoxyd  of 
iron  12'1,  soda  10'5.  Analysis  of  El  Paso  County  mineral  by  Konig  was 
published  in  the  proceedings  of  the  American  Philosophical  Society  of 
Philadelphia. 

Occurs  at  St.  Peter's  Dome,  El  Paso  County,  with  astroph- 
yllite,  zircon,  etc. 

GAHXITB.     Zinc-Spinel.     Oenth,  Am.  Phi.  Soc. 

Isometric;  occurs  in  octahedrons  and  dodecahedrons.  Lustre  vitreous  or 
somewhat  greasy.  Color  dark  green.  grayish  -green,  deep  leek-green,  green- 
ish-black, bluish,  black,  yellowish,  grayish-brown.  Subtranslucent  to 
opaque.  H.  7'5-8.  G.  4-4-6.  Comp.,  alumina  61'3,  oxyd  of  zinc  38*7. 

Large  rough  crystals  occur  in  the  Cotopaxi  mine,  Chaftee 
County. 

TOPAZ.     Cross  and  Hittebrand,  Am.  Jr.  Sc.,  Oct.,  1882;  Bui.  20,  U.  8.  Geo. 

Sur.     W.  B.  Smith,  Bui.  U.  S.  Geo.  Sur. 

Orthorhombic  ;  primary  form  right  rhombic  prism;  crystals  usually  hemi- 
hedral,  the  extremes  being  unlike.  Cleavage  perfect  at  right  angles  to  the 
principal  axis  ;  also  occurs  fine  columnar,  granular,  coarse  or  fine.  Lustre 
vitreous.  Color  straw-yellow,  wine-yellow,  white,  grayish,  greenish,  blu- 
ish, reddish.  Transparent  to  subtranslucent.  Pyroelectric.  H.  8.  G. 
3*4-3*65.  Analysis  of  Florissant  specimen  by  Hillebrand  :  silica  33'15, 
alumina  57'01,  fluorine  16'04,  oxygen  for  fluorine  6*75. 

Found  in  Crystal  Park,  south  of  Manitou,  in  cavities  in 
granite  containing  feldspars,  smoky  quartz,  zircon  and  phena- 
cite;  at  the  main  amazonstone  locality  near  Florissant  :  and, 
more  plentifully  and  in  better  form  than  elsewhere,  on  Devil's 
Head  Mountain,  Douglas  County.  In  small  crystals  in  the 
nevadite  from  Chalk  Mountain,  where  Lake,  Eagle  and  Sum- 
mit Counties  join.  A  fragment  of  a  crystal  3J  in.  in  its  long- 
est diameter,  was  found  near  Florissant,  which  evidently 
came  from  a  crystal  about  one  foot  in  diameter.  It  is  clear 
in  parts  and  has  a  decided  greenish  tinge.  It  was  supposed 
to  be  fluor  spar  by  the  original  collectors,  and  the  other  pieces 
of  the  crystal  are  undoubtedly  lost.  Crystals  are  also  found 
in  this  locality  deposited  upon  or  partially  imbedded  in  am- 
azonstone, albite,  etc.  In  size  the  crystals  vary  from  a  length 
of  nearly  two  inches  to  those  which  are  almost  microscopic. 
Some  of  the  crystals  have  a  decided  greenish  tinge,  although 
many  are  colorless.  The  topaz  found  at  Devil's  Head  Moun- 
tain also  occur  in  cavities  with  amazonstone,  smoky  quartz, 
and  other  minerals,  and  are  the  most  noteworthy  crystallized 
species,  some  of  the  specimens  found  being  probably  the  best 
yet  discovered  in  the  United  States.  Much  of  the  topaz  is 
reddish,  though  wine-yellow,  milk-blue,  and  colorless  crystals 
are  found.  Quite  perfect  and  clear  crystals  have  been  found 
weighing  from  five  to  six  ounces. 


Minerals  of  Colorado.  23 

KAL,IN1TK.     Potash  Alum.     Native  Alum. 

Isometric ;  usually  fibrous  or  massive,  or  in  inealy  or  solid  crusts.  Lustre 
vitreous.  Color  white.  Transparent — translucent.  H.  2-2'5.  G.  1'75. 
Comp.,  sulphate  of  potash  18*4,  sulphate  of  alumina  36'2,  water  45'5 

Occurs  as  an  efflorescence  on  argellaceous  rocks  at  Canon 
City,  on  Turkey  Creek,  Little  Thompson  Creek,  and  in  small 
quantities  in  various  localities  along  the  "hog-back. " 

STIBNITE.     Antimony  Glance.     Sulphuret  of  Antimony. 

Orthorhombic ;  primary  form  a  right  rhombic  prism  ;  occurs  crystallized 
in  variously  modified  and  terminated  rhombic  prisms,  which  are  some- 
times closely  aggregated  laterally ;  lateral  planes  of  crystals  deeply  stri- 
ated longitudinally  ;  also  occurs  columnar,  coarse  or  fine;  also  granular  to 
impalpable.  Color  and  streak  lead-gray  ;  inclining  to  steel-gray;  subject 
to  blackish  tarnish.  Lustre  metallic.  Sectile.  Thin  lamina  a  little  flex- 
ible. H.  2.  G.  4-51-4-62.  Comp.,  sulphur  28*2,  antimony  71'8. 

Occurs  crystallized  in  the  North  Star  mine,  Sultan  Moun- 
tain, near  Silverton. 

QUARTZ. 

Rhombohedral ;  occurs  in  hexagonal  prisms,  sometimes  terminated  at  both 
ends  by  six-sided  pyramids.  Colorless  when  pure  ;  various  shades  of  yel- 
low, red,  brown,  green,  blue,  violet  and  black.  Transparent  to  opaque. 
Lustre  vitreous,  sometimes  inclining  to  resinous.  Fracture  conchoidal. 
Tough,  brittle,  friable.  H.  7.  G.  2'5-2"8.  Comp.,  pure  silica,  or,  oxygen 
53-33,  silicon  46 '67. 

Quartz  is  a  constituent  of  many  rocks,  and  composes  most 
of  the  pebbles  of  gravel  beds.  It  takes  on  more  forms  and 
colors  than  any  other  mineral,  and  is  divided  into  three  va- 
rieties, the  vitreous,  chalcedonic  and  jaspery.  Vitreous  vari- 
eties are  distinguished  by  their  glassy  fracture  ;  chalcedonic 
varieties  by  having  a  subvitreous  or  waxy  lustre,  and  gener- 
ally translucent ;  the  jaspery  varieties  are  opaque. 

ROCK  CRYSTAL. 

Pure  pellucid  quartz.    Usually  occurs  in  six-sided  crystals. 

Clear  crystals,  some  of  which  are  doubly  terminated,  are 
found  near  Maysville.  Large  crystals  in  the  Blk  mountains. 
Pellucid  water- worn  nodules  in  the  gravel  of  Platte  River. 
Common  as  drusy  incrustations  in  the  mines.  Rock  crystal 
is  made  into  lenses  for  spectacles,  and  is  known  as  Scotch  and 
Brazilian  Pebbles.  The  so-called  Alaska  and  California  dia- 
monds are  cut  from  rock  crystal. 

AMETHYST. 

Quartz  of  a  clear  purple  or  violet-blue  color,  of  various  degrees  of  intensity. 
The  color  is  supposed  to  be  derived  from  manganese. 

Fine  specimens  have  been  met  with  in  the  veins  near  Du- 
mont.  Small  crystals  at  Nevada  and  Black  Hawk.  On  Grape 
Creek,  Fremont  County.  In  the  Elk  mountains.  In  geodes 
on  the  Rio  Grande  River.  Occasionally  in  South  Park,  asso- 
ciated with  smoky  quartz,  amazonstone  and  gothite. 


24  Minerals  of  Colorado. 

ROSE  QUARTS. 

A  transparent,  or  nearly  transparent  variety  of  quartz,  of  a  rose-red  or 
pink  color.     It  usually  occurs  massive,  and  often  much  fractured. 

Occuas  in  large  masses  at  the  summit  of  Floyd  Hill  ;    near 
Central  City;  on  Bear  and  Soda  Creeks. 


QUARTZ.     False  Topaz.     Citrine. 
Color  lemon-yellow,  golden,  or  wine-yellow. 

Found  in  the  gravel  on  the  divide  between  the  Platte  and 
Arkansas,  about  the  head  of  Plum  Creek.  On  the  west  slope 
of  Pike's  Peak,  near  its  base. 

CAIRNGORM.     Smoky  Quartz.     Morion. 

Color  various  shades  of  brown,  passing  into  black.    * 

Abundant  about  Florissant,  El  Paso  County,  where  it 
occurs  in  "pockets"  in  the  granite,  associated  with  amazon- 
stone,  albite,  gothite  and  fluorite.  Some  of  the  crystals  are 
of  great  size  and  extreme  beauty.  One  crystal  was  found 
which  measured  4^  feet  in  length  and  10  inches  in  diameter 
at  the  base.  A  great  many  have  been  found  from  20  to  30 
inches  in  length.  The  crystals  are  usually  transparent,  and 
have  been  used  quite  extensively  in  the  manufacture  of  jew- 
elry. Smoky  quartz  is  also  found  at  the  head  of  Plum  Creek  ; 
in  the  neighborhood  of  Larkspur,  Summit  and  Monument; 
at  the  head  of  Beaver  Creek;  on  Cheyenne  mountain;  Elk 
Creek,  and  in  the  nevadite  of  Chalk  mountain. 

JASPER. 

Impure  opaque  colored  quartz.  The  most  common  colors  are  brown,  red 
and  yellow.  Called  Ribbon  Jasper  when  the  colors  are  in  broad  stripes  or 
bands.  Egyptian  Jasper  when  the  colors  appear  in  zones. 

Red  and  yellow  jasper  is  found  very  plentifully  in  Middle 
and  South  Parks.  A  large  proportion  of  the  petrified  wood 
on  the  Platte  and  Arkansas  divide,  is  jasper.  Along  the 
sources  of  Cherry,  Kiowa,  and  Bijou  Creeks,  it  is  quite  com- 
mon to  find  large  trees,  60  or  70  feet  in  length,  changed  to 
jasper.  Ribbon  Jasper  is  found  near  Larkspur  ;  also  in  Mid- 
dle Park,  at  the  junction  of  the  Willow  and  Grand,  in  dark 
green  and  yellow  stripes.  Egyptian  Jasper  near  Larkspur. 

CERARGYRIXE.     Horn  Silver.     Chloride  of  Silver. 

Isometric;  occurs  crystallized  in  small  cubes  and  acicular  prisms;  gener- 
ally massive  and  looking  like  wax;  sometimes  columnar,  or  bent  col- 
umnar; often  in  crusts.  Lustre  resinous,  passing  into  adamantine.  Color 
pearl-gray,  grayish-green,  whitish,  rarely  violet-blue,  colorless  sometimes 
when  perfectly  pure  ;  brown  or  violet-brown  on  exposure.  Streak  shining. 
Transparent  —  feebly  translucent.  Fracture  somewhat  conchoidal.  Sectile. 
Comp.,  Chlorine  247,  silver  75'3. 

Common  in  the  mines  of  Leadville,  Silver  Cliff  and  Rosita. 
Occasionally  found  near  the  surface  of  veins  about  George- 
town and  elsewhere. 


Minerals  of  Colorado.  25 

CEXESTITE.     Fibrous  Heavy  Spar.    Sulphate  of  Strontia. 

Orthorhombic;  in  modified  rhombic  prisms;  crystals  sometimes  flattened; 
often  long  and  slender;  also  fibrous  and  radiated;  sometimes  globular; 
occasionally  granular.  Lustre  vitreous,  sometimes  inclining  to  pearly. 
Color  white,  often  bluish,  and  sometimes  reddish.  Streak  white.  Trans- 
parent —  subtranslucent.  Brittle.  Trichroism  sometimes  very  distinct. 
Phosphoresces  when  heated.  H.  3-3'5.  G.  3'92-3-95'  Comp.,  sulphuric 
acid  43'6,  strontia  56'4. 

Occurs  as  nodules  in  the  Garden  of  trie  Gods,  which,  upon 
being  broken,  present  a  mass  of  beautiful  blue  crystals;  occa- 
sionally in  fibrous  masses.  Celestite  is  used  in  the  arts  for 
making  nitrate  of  strontia,  which  is  employed  for  producing 
a  red  color  in  fire  works. 

SPHALtKRITK.     Blende.     Zinc-Blende.     Sulphuret  of  Zinc. 

Isometric;  tetrahedral  ;  occurs  crystallized  and  amorphous;  botryoidal 
and  other  imitative  shapes;  sometimes  fibrous  and  radiated  ;  also  massive, 
compact.  Cleavage,  dodecahedral,  highly  perfect.  Color  brown,  yellow, 
black,  red,  green  ;  white  or  yellow  when  pure.  Lustre  resinous  to  ada- 
mantine. Streak  white  to  reddish-brown.  Transparont  to  translucent. 
Fracture  conchoidal.  Brittle.  H.  3'5-4.  G.  3'9-4'2.  Comp.,  sulphur  33, 
zinc  67. 

Common  in  many  of  the  gold  and  silver  mines,  and  fre- 
quently rich  in  gold  or  silver,  although  usually  of  but  small 
value.  Fine  cabinet  specimens  of  black  blende  in  the  Maine 
and  other  mines  about  Georgetown  ;  in  the  Coaley,  Calhoun 
and  Delaware  lodes,  Gilpin  County  ;  beautiful  green  crystals 
in  the  L/ittle  Giant  lode,  near  L/awson,  Clear  Creek  County. 


Sulphuret  of  Molybdena. 
Hexagonal  ;  occurs  in  flat  hexagonal  tables,  with  a  cleavage  parallel  to 
their  terminal  planes  ;  generally  massive  with  a  foliated  structure,  or'in 
scales.  Color  pure  lead-gray.  Lustre  metallic.  Streak  similar  to  color, 
slightly  inclining  to  green.  Laminae  flexible,  but  not  elastic.  Sectile,  and 
almost  malleable.  Leaves  a  gray  trace  on  paper,  a  greenish  trace  on  por- 
celain. H.  1-1*5,  being  easily  impressed  by  the  nail.  G.  4'4-4'8.  Comp., 
sulphur  41,  molybdenum  59. 

About  Georgetown  ;  Rock  Creek,  Gunnison  County  ;  Boul- 
der, Gilpin  and  Summit  counties.  Salts  'of  molybdenum  are 
used  to  some  extent  in  chemical  operations. 

HALITE.  Common  Salt.  Kock  Salt.  Muriate  of  Soda.  Chlorid  of  Sodium. 
Isometric;  usually  occurs  in  cubical  crystals;  rarely  in  octahedrons; 
faces  of  crystals  sometimes  cavernous.  Massive  and  granular,  rarely  col- 
umnar. Cubic  cleavage.  Lustre  vitreous.  Color  white,  sometimes  yel- 
lowish, reddish,  bluish,  purplish  ;  often  colorless.  Transparent  —  translu- 
cent.* Fracture  conchoidal.  Rather  brittle.  Soluble.  Taste  purely 
saline.  H.  2'5.  G.  2'l-2'257.  Comp.,  chlorine  607,  sodium  39'3,  com- 
monly mixed  with  some  sulphate  of  lime,  chlorid  of  calcium,  etc. 

Occurs  in  solution  and  as  an  incrustation  about  the  salt 
springs  in  South  Park.  Works  were  erected  about  1868,  and 
considerable  salt  manufactured,  but  the  company  got  into  lit- 
igation, and  the  works  were  abandoned. 


26  Minerals  of  Colorado. 

GYPSUM.     Sulphate  of  Lime. 

Monoclinic;  crystals  usually  in  right  rhomboidal  prisms,  with  beveled 
sides;  frequently  the  shape  of  an  arrow-head  ;  eminently  foliated  in  one 
direction,  and  cleaving  easily,  affording  laminae  that  are  flexible  but  not 
elastic;  crystallized  variety  called  selenite.  Also  occurs  in«  laminated 
masses  ;  fibrous,  with  a  satin  lustre  (satin-spar)-  in  stellated  or  radiating 
forms,  consisting  of  narrow  laminae;  also  granular  and  compact  (alabaster). 
Color  usually  white;  'sometimes  gray,  yellow,  reddish,  brown,  black. 
Streak  white.  Transparent — opaque.  H.  l'5-2.  G.  2'3.  Comp.,  sulphu- 
ric acid  46'5,  lime  32'6,  water  20'8. 

Occurs  in  large  beds  of  great  purity  in  the  South  Park  and 
along  the  base  of  the  mountains;  specially  available  at  Mor- 
rison and  Colorado  Springs,  where  mills  have  been  built  for 
the  manufacture  of  gypsum  into  plaster-of-paris. 

SEUENITK.     Crystallized  variety  of  Gypsum. 

Occurs  either  in  distinct  crystals,  or  broad  folia,  the  folia  sometimes  a  yard 
across,  and  transparent  throughout.  Cleaves  easily,  the  plates  bending  in 
one  direction. 

Occurs  in  grouped  and  single  crystals  on  Box  Elder  Creek, 
Ivaramie  County ;  at  River  Bend,  on  the  K.  P.  Railway,  in 
fine  crystals ;  on  Bear  Creek,  near  Morrison.  Selenite,  in 
thin  folia,  was  formerly  extensively  used  in  windows,  and  is 
still  used  for  that  purpose  by  the  Mexicans  in  the  Socorro 
mountains. 

SATIN  SPAR.     Fibrous  Gypsum. 

Occurs  in  fine  fibrous  masses,  having  a  satin  lustre,  and  the  pearly  opales- 
cence  of  the  moonstone. 

Fine  white  masses  at  Morrison.  Pink  and  white  near 
Quick's  ranch,  on  Plum  Creek.  Satin  Spar  is  used  in  the 
manufacture  of  beads  and  other  ornamental  articles. 

ALABASTER.     Granular  Gypsum. 

Fine-grained,  and  either  white  or  delicately  shaded. 

On  Box  Elder  Creek,  in  immense  deposits.  At  Morrison, 
white  and  mottled.  At  Colorado  Springs,  pink  and  white. 
At  Canon  City,  pure  white. 

GADOI^INITB.     Eakins,  Proc.  Colo.  Sc.  Soc.,  1885. 

Orthorhombic;  in  oblique  rhombic  prism;  occurs  also  in  small  masses. 
Color  black,  greenish-black  ;  dull  externally,  internally  shining;  in  thin 
splinters  nearly  transparent,  and  grass-green  to  olive-green.  Streak  green- 
ish-gray. Lustre  vitreous.  Subtranslucent — opaque.  Fracture  conch- 
oidal.  H.  6'5-7.  G.  4-4'5.  Analysis  of  Colorado  mineral  by  Eakins: 
Silica  22'13,  alumina  2'34,  protoxyd  of  iron  T13,  thoria  Q'&9,  oxide  of 
cerium  ll'lO,  oxide  of  lanthanum  and  didymium  21/23,  erbium  12'74, 
yttria  9'50,  oxide  of  iron  10'43,  beryllium  7'19,  lime  0'34,  magnesia  0' 14, 
potassa  0'18,  soda  0'28,  water  0'86. 

Occurs  in  small  fragments  on  Devil's  Head  mountain, 
Douglas  County.  This  is  the  first  observed  occurrence  of  the 
mineral  in  this  country,  and  was  found  by  Mr.  W.  B.  Smith, 
of  the  U.  S.  Geological  Survey. 


Minerals  of  Colorado.  27 

Silicate  of  Zinc. 

Orthorhorabic  ;  occurs  in  obtuse  rhorabohedrons,  and  in  long  quadrilateral 
tables;  also  stalactitic,  mammilated,  botryoidal,  fibrous,  massive  and  gran- 
ular. Lustre  subpearly,  sometimes  adamantine.  Color  white  ;  sometimes 
with  a  delicate  bluish  or  greenish  shade  ;  also  yellowish  to  brown.  Streak 
white.  Transparent  —  translucent.  Brittle.  Fracture  uneven.  Pyroelec- 
tric.  Double  refraction  strong.  H.  4'5-5.  G.  3'16-3'49.  Comp.,  silica 
25'0,  oxyd  of  zinc  67'5,  water  7'5. 

Occurs  as  a  delicate  white   incrustation   in  the  mines  of 
Leadville. 


H.  F.  and  H.  A.  Kellar,  Am.  Ghent.  Jr.,  vol.  2. 
Radiated  structure.     Color  dark  lead-gray.     Lustre  bright.    Soft.    G.  6'29. 
Analysis  of  mineral  from  Lillian  Co's  mines:  sulphur  15'21,  bismuth  32'62, 
lead  43'94,  silyer  5*78,  copper  trace. 

Occurs  in  the  mines  of  the  Lillian  company  on  Printer  Boy 
Hill,  near  Leadville,  in  nodules  of  various  sizes  up  to  several 
feet  in  diameter,  more  or  less  oxidized.  The  fresh  mineral 
has  a  fine-grained  crystalline  structure,  and  steel-gray  color. 

GRAPHITE.     Plumbago.     Black  Lead. 

Hexagonal  ;  in  flat  six-sided  tables.  Commonly  in  imbedded,  foliated,  or 
granular  masses.  Perfect  cleavage.  Color  iron-black  to  dark  steel-gray. 
Streak  black  and  shining.  Lustre  metallic.  Soils  paper.  Sectile  ;  thin 
laminae  flexible.  Feel  greasy.  H.  1-2.  G.  2'0891.  Comp.,  pure  carbon, 
with  often  a  little  oxyd  of  iron  mechanically  mixed. 

At  Pitkin,  in  beds  2  feet  thick;  large  masses  at  Trinidad; 
small  veins  at  Maysville,  but  very  impure  in  each  locality. 
Graphite  is  largely  employed  under  the  name  of  Plumbago, 
or  Black  Lead,  for  the  manufacture  of  crucibles  and  other  re- 
fractory articles  ;  foundry  facings,  lubricating  compounds, 
electrical  supplies,  stove-polish,  pencil  leads  and  pigments. 
It  has  an  average  spot  value  of  8  cents  a  pound. 

SCHEEUTTE.     Tungstate  of  Lime.    Sittiman,  Am.  Jr.  Sc.,  June,  1877. 

Tetragonal  ;  primary  form  a  right  square  prism  ;  occurs  in  attached  and 
imbedded  four-sided  pyramids,  approaching  nearly  to  the  octahedron  ;  also 
occurs  reniforrn  with  columnar  structure,  and  massive  granular.  Lustre 
vitreous  inclining  to  adamantine.  Color  white,  yellowish-white  to  orange. 
yellow,  brownish,  greenish.  Streak  white.  Transparent  to  translucent, 
H.-  4-5-5.  G.  5'9.  Comp.,  lime  19'4,  tungstic  acid  80'6. 

Gold-bearing  scheelite  occurs  in  the  Golden  Queen  mine, 
Lake  County. 


Silicate  of  Vanadium.  Genth,  Am.  Phi.  Soc.,  Phila.,  1877. 
Micaceous  in  structure;  scales  minute,  often  arranged  in  stellate  or  fan  - 
shaped  groups.  Basal  cleavage  perfect.  Color  dark  clover-brown  to 
greenish-brown.  Analysis  of  Boulder  County  mineral  by  Genth  :  silica 
56-74,  alumina  19'62?  vanadium  7'78,  iron  oxide  3'84,  magnesia  2'63,  po- 
tassa  8'11,  with  traces  of  manganese,  soda,  lithium  and  water. 

In  the  mines  of  Magnolia  District,  Boulder  County,  as  a 
thin  earthy  incrustation  of  a  grayish  to  olive-green  color  on 
calaverite;  also  inclosed  in  quartz,  and  giving  it  a  green  color. 


28  Minerals  of  Colorado. 

HESSIXE.     Telluric  Silver.    Silliman,  Am.  Jr.  Sc.,  July,  1874.     Genth,  Am. 

Phi.  Soc.,  1874. 

Orthorhombic  ;  massive ;  compact  or  fine-grained  ;  rarely  coarse  granular. 
Lustre  metallic.  Color  between  lead-gray  and  steel-gray.  Sectile  and 
malleable,  laminating  into  thin  scales  under  the  pestle,  leaving  on  the 
agate  surfaces  metallic  streaks  of  plumbago-like  color.  H.  2-3*5.  G.  8*3 
8'6.  Analysis  by  Genth  of  mineral  from  the  Red  Cloud  mine,  Boulder 
County  :  gold  0*22,  silver  59;91,  copper  017,  lead  0.45,  zinc  trace,  iron  1/35, 
tellurium  37*86.  An  auriferous  variety  gave:  gold  13*09,  silver  50'36,  tel- 
lurium 34-91.  * 

Occurs  abundantly  in  the  Slide  and  Prussian  mines,  and 
sparingly  in  other  mines  at  Gold  Hill  and  Sunshine,  Boulder 
County. 

"WOlrFR.  AMITK.     Tungstate  of  Manganese. 

Orthorhombic ;    primary  form  a  right  rhombic  prism ;  occurs  massive  and 
crystalized  ;  irregular  lamellar ;  coarse  divergent  columnar ;  massive  gran- 
ular, the  particles  strongly   coherent.     Lustre  submetallic.     Color  dark 
grayish  or  brownish  black.     Streak  dark  reddish  brown  to  black.     Some- 
times weak  magnetic.     H.  5-5*5.     G.  7*1-7*55.     Comp.,  tungstic  acid  75*92, 
Srotoxide  of  iron  19*35,  protoxide  of  manganese  4*73. 
ebrand  mentions  its  occurrence  in  the  Missouri  mine, 
Hall  Valley,  Park  County,     Occurs  near  Boulder. 

UR.ANINITE.  Pitchblende.  Protoxyd  of  Uranium.  Am.  Jr.  Sc.,  1873. 
Isometric ;  usually  massive  and  botryoidal ;  also  in  grains.  Structure 
sometimes  columnar,  or  curved  lamellar.  Lustre  submetallic  to  greasy  or 
pitch-like,  and  dull.  Color  grayish,  greenish,  brownish,  velvet-black. 
Streak  brownish,  a  little  shining.  Fracture  conchoidal,  uneven.  H. 
5*5.  G.  6*4-8.  Comp.,  protoxyd  of  uranium  32*1,  sesquioxyd  67*9,  but 
analyses  vary  much  through  mixture  with  other  substances. 

A  pocket  of  uraninite  was  encountered  in  the  Wood  lode, 
Central  City, in  1873, nearly  all  of  which  was  shipped  to  Eng- 
land by  Kichard  Pearce,  esq.,  of  the  Boston  and  Colorado 
Smelter,  and  sold  for  $1.50  per  pound.  Thin  seams  of  the 
mineral  occur  in  Jefferson  county.  A  mass  of  uraniuite 
was  encountered  in  the  Jo  Reynolds  mines,  Clear  Creek 
County,  in  1885,  but  unfortunately,  it  was  mixed  with  the 
silver  pre  from  the  mine,  and  milled,  the  adulteration  caus- 
ing a  serious  loss  to  the  miners.  But  two  or  three  specimens 
were  saved,  one  of  which  is  in  the  collection  of  the  compiler, 
also  specimens  from  the  Wood  lode. 

Uranium  has  the  color  and  lustre  of  silver,  but  is  harder, 
and  gives  out  sparks  when  struck  with  a  hammer.  It  oxid- 
izes gradually  when  exposed  to  the  air,  burns  when  heated 
on  platinum-foil,  and  is  dissolved  by  nitric  acid.  Its  specific 
gravity  is  18*7.  Its  compounds  are  used  in  considerable 
quantities  in  chemical  operations  and  in  porcelain  painting, 
affording  a  yellow  or  black  color,  according  to  the  process  of 
baking. 


Minerals  of  Colorado.  29 

Telluride  of  Gold.  Genth,  Am.  Phi.  Soc.^  Phila.,  1877. 
Occurs  massive  and  in  small  crystals.  Color  bronze-yellow.  Streak  yel- 
lowish-gray. Brittle.  Fracture  uneven,  inclining  to  subconchoidal.  Anal- 
ysis of  Colorado  mineral  by  Genth:  tellurium  57'32,  gold  38'75,  silver 
3*03,  oxyd  of  vanadium  0'05,  protoxyd  of  iron  0'03,  alumina,  magnesia,etc., 
0-55,  quartz  4'96.  Theoretical  formula,  tellurium  57'93,  gold  39'01,  sil- 
ver 3'C6. 

In  the  Slide,  Keystone  J  Mountain  Lion  and  other  mines,  in 
Boulder  County.  Small  imperfect  crystals  imbedded  in 
quartz. 


(new.}    Genth,  Am.  Phi.  Soc.  Phil.,  1877. 
Tn  delicate  radiating  tufts  ;    also  in  very  minute  prismatic  crystals.     Color 
between  straw  and  lemon-yellow,  inclining  to  greenish-yellow.     Contains 
iron  and  tellurium. 

Found  as  a  coating  on  quartz  associated  with  native  tellu- 
rium and  tellurite,  at  ihe  Keystone  mine,  Magnolia  District, 
Boulder  County. 


(new.)     Variety  of  Native  Tellurium.      Genth,  Am.  Phi.  Soc. 
Phil.,  1877. 

Occurs  in  thin  plates.  Color  dark  gray.  H.  3.  G.  4'005.  Analysis  of 
Colorado  mineral  by  Genth  :  tellurium  55'54,  quartz  35'91,  alumina  and 
iron  oxyd  6'14,  manganese  and  iron  oxide  0*19,  calcium  and  iron  oxide 
0-26,  gold  1-53,  silver  0'25. 

Occurs  in  the  Mountain  Lion  mine,  Boulder  County,  from 
which  it  was  named  by  Berdell. 


(new).  Telluride  of  Mercury.  Genth,  Am.  Phi.  Soc.,  1877. 
Occurs  in  radiating  tufts  of  very  minute  acicular  or  capillary  crystals. 
Color  white.  Lustre  silky.  Contains  mercury  and  tellurium. 

Qccurs  as  a  product  of  the  decomposition  of  coloradoite  in 
the  upper  part  of  the  Keystone,  mine,  Magnolia  District,  Boul- 
der County.  Named  from  Magnolia  District. 


Tellurious  Acid.     Genth,  Am.  Phi.  Soc.  Phil.,  1877. 
Occurs  in  prismatic  crystals  and  in  spherical  masses,  radiated  in  structure  ; 
also  as  an  incrustation.     Crystals  cleavable  in  one  direction.     Color  yellow 
to  white. 

In  the  John  Jay  mine,  Boulder  County,  as  an  incrustation 
in  cracks  in  native  tellurium,  and  in  minute  prismatic  crys- 
tals. 

CHRYSOCOLLA.    Silicate  of  Copper. 

Cry  ptocrystal  line  ;  often  opal-like  or  enamel-like  in  texture;  earthy;  in- 
crusti/ig  or  filling  seams;  sometimes  botryoidal.  Color  various  shades  of 
blue,  passing  into  green.  Streak,  when  pure,  white.  Translucent  to 
opaque.  Fracture  conchoidal.  H.  2-4.  G.  2'2.  Comp.,  silica  34'2,  oxyd 
of  copper  45'3,  water  20'5.  An  analysis  by  Genth  of  what  was  supposed 
to  be  chrysocolla,  from  Bergen  Park,  gave  33.85  alumina,  and  5'40  of  cop- 
per oxide,  which  corresponds  to  allophane  with  probably  some  chrysocolla. 

Found  in  copper  lodes  on  Bear  Creek;  near  Canon  City  ; 
at  the  head  of  San  Luis  Valley;  in  the  Champion  lode,  Idaho 
Springs,  and  in  small  quantity  in  many  other  localities. 


30  Minerals  of  Colorado. 


Cobalt  Bloom.  Ked  Cobalt  Ore.  Cobalt  Ochre.  W.  F. 
Hillebrand,  Am.  Jr.  Sc.,  May,  1884  ;  Proc.  Col.  Sic.  Soc.,  Vol.  I. 
Monoclinic;  in  acicular  diverging  crystals,  modified  at  the  edges,  and 
whose  form  is  a  right  oblique-angled  prism  ;  also  found  in  globular  and 
reniform  shapes,  having  a  drusy  surface  and  a  columnar  structure;  some- 
times stellate;  also  pulverulent  and  earthy,  incrusting.  Lustre  vitreous 
to  earthy.  Color  crimson  and  peach-red,  sometimes  pearly  or  greenish- 
gray  ;  red  tints  incline  to  blue  perpendicular  to  cleavage  face.  Streak  a 
little  paler  than  the  color;  the  dry  powder  deep  lavender-blue.  Thin 
laminae  flexible  in  one  direction.  Sectile.  H.  rS-2'5,  G.  2'94.  Comp., 
arsenic  acid  38'43,  oxyd  of  cobalt  37*55,  water  24'02. 

A  product  of  the  alteration  of  lollingite  in  the  mines  on 
Teocalli  Mountain,  Brush  Creek,  Gunnison  County. 

AMPHIBOUE.     Hornblende. 

Monoclinic;  crystals  often  long  and  bladed,  sometimes  stout;  fibrous,  col- 
umnar, coarse  or  fine,  fibers  often  like  flax,  when  it  is  known  by  other 
names.  Color  between  black  and  white,  through  various  shades  of  green, 
inclining  to  blackish  green.  This  species  has  numerous  varieties,  differing 
much  in  external  appearance  and  in  composition.  Silica,  alumina,  lime, 
iron  and  magnesia  enter  into  the  composition. 

Hornblende  is  an  essential  constituent  of  many  of  the  rocks 
of  the  mountainous  region,  such  as  hornblende  gneiss,  a 
tough  dark  rock,  which  is  quite  abundant,  seyenitc,  trap.,  etc, 
It  is  occasionally  found  massive  and  crystallized. 

ASBESTOS.     A  variety  of  Amphibole. 

Occurs  in  fine  fibrous  masses,  of  light  color. 

In  the  Star  of  the  West  and  other  lodes  at  the  head  of 
of  North  Boulder  Creek,  Boulder  County,  associated  with 
galena.  Near  Maysville,  Chaffee  County,  in  mineral  veins. 

Asbestos  was  woven  into  cloth  by  the  ancients,  which,  from 
its  incombustibility,  was  used  to  wrap  the  bodies  of  the  dead 
before  placing  them  on  the  funeral  pile,  by  which  the  ashes 
were  preserved  for  subsequent  preservation  in  vases.  Cloth- 
ing was  manufactured  from  it,  which  was  cleansed  by  burn- 
ing instead  of  washing.  Its  chief  use  now  is  for  making  tire- 
proof  roofing,  boiler  lining  and  lire  proof  safes. 

TttEMOUTti. 

The  name  given  to  the  white  or  light  greenish  variety  of  Amphibole.  It 
occurs  in  long  slender  blades,  or  in  columnar  and  radiated  aggregations. 

In  white,  radiated  masses  near  Maysville,  Chaffee  County. 

ACXIJJOWTE.     A  variety  of  Amphibole. 

Fibrous,  columnary  or  massive.     Color  bright  green  or  grayish-green. 

On  Bear  Creek,  Jefferson  County,  in  fibrous  aggregations, 
of  a  dark  green  color.  In  the  mineral  veins  at  the  head  of 
North  Boulder  Creek,  and  in  the  Partridge  lode,  on  Coal 
Creek,  Boulder  County.  Light  green  and  bluish-green  on 
Mount  Ouray.  Specimens  of  the  amphibole  minerals  in  the 
compiler's  collection. 


Minerals  of  Colorado.  31 

(new.}    Telluride  of  Mercury.     Genth,  Am.  Phi.  Soc., 
Phtta.,  1877. 

Massive  ;  granular,  sometimes  imperfectly  columnar  (due  to  admixed  syl- 
vanite?)  Luster  metallic.  Color  iron-black  inclining  to  gray.  Fracture 
uneven  to  subconchoidal.  Theoretical  composition,  tellurium  39'02,  mer- 
cury 60*98.  Analyses  of  mineral  from  the  Keystone  and  Smuggler  mines 
by  Genth,  varied  a  great  deal  on  account  of  an  admixture  of  gold  and 
quartz.  That  from  the  Keystone  mine  carried  Irom  8  to  46  per  cent  of 
gold  and  quartz,  with  small  amounts  of  alumina,  iron,  vanadium  and  mag- 
nesia. Mineral  from  the  Smuggler  mine  contained  quartz  and  gold,  3'05, 
tellurium  34*49,  mercury  48*74,  gold  7*67,  silver  7*18,  iron  0*92,  copper  0*16, 
zinc  0-50.  H.  3.  G.  8'627. 

Occurs  sparingly  in  the  Keystone,  Smuggler  and  Mountain 
Lion  mines,  Boulder  county. 


Soda  Alum. 

Occurs  in  white  fibrous  and  pulverulent  masses.  Resembles  fibrous  gyp- 
sum, but  harder.  H.3.  G.  1'88.  Reported  analysis  of  Colorado  mineral  : 
sulphuric  acid  38*35,  sulphate  of  alumina  14'66,  sulphate  of  soda  4*35 
water  42*64. 

F.  F.  Chisolmn  reports  its  occurrence  in  a  lode  one-and-a- 
half  miles  shuth-east  of  Red  Cliff. 


Anhydrous  Silicate  of  Zinc. 
Rhombohedral  ;  occurs  in  regular  six-sided  prisms;  also  massive,  fibrous 
and  in  grains.  Color  whitish,  yellowish,  flesh-red,  apple-green  and  dark- 
brown.  Streak  same  as  color.  Luster  vitreo-resinous.  Transparent  to 
opaque.  Brittle.  Fracture  coochoidal.  Double  refracting.  H.  5*5.  G. 
3-84-4*18.  Comp.,  silica  27*1,  oxyd  of  zinc  72*9. 

Occurs  sparingly  at  the  head  of  the  Rio  La  Plata  as  a  pale 
green  crystalline  mineral  filling  cavities  in  other  zinc  ores. 


(new.)     Sulphate  of  Manganese.    M.  W.  lies,  American  Chemical 
Journal,  1881. 

Occurs  in  thick  prisms  which  are  frequently  terminated  by  truncated  pyr- 
amids. Friable.  Taste  bitter,  astringent.  Color  white.  Soft.  G.  2*16. 
Analysis  by  lies:  protoxyd  of  iron  4*18,  oxyd  of  zinc  5*97,  protoxyd  of 
manganese  22*31,  sulphuric  acid  36*07,  water  31*60. 

Occurs  in  veins  from  two  to  eight  inches  wide  in  the  Mc- 
Donnell lode,  Middle  Swan  Creek,  Hall  Valley,  Park  county. 
Named  after  Dr.  M.  W.  lies. 

CHAI.CAN'THITB.     Blue  Vitriol.    Sulphate  of  Copper. 

Triclinic;  rarely  found  in  distinct  crystals;  generally  occurs  stalactitic, 
reniform,  amorphous  and  pulverulent.  Color  Berlin-blue  to  sky-blue  of 
various  shades  ;  sometimes  greenish  ;  turns  white  on  exposure.  Translu- 
cent. Luster  vitreous.  Taste  metallic  and  nauseous.  Comp.,  sulphuric 
acid  32-1,  oxyd  of  copper  31*8,  water  36*1. 

Occurs  in  a  number  @f  mines  in  Hall  Valley,  Park  county; 
in  the  Whale  tunnel,  near  Idaho  Springs;  in  a  deposit  below 
Black  Hawk.  It  is  formed  by  the  decomposition  of  iron  and 
copper  pyrites.  When  purified  it  is  employed  in  cotton  and 
linen  printing,  and  for  various  other  purposes  in  the  arts.  It 
is  sometimes  employed  to  prevent  dry  rot  in  wood. 


32  Minerals  of  Colorado. 

SCHIR.MBR.IXE.    (new.)     Bismuth  Silver.     F.  A.  Genth,  Proc.  Am.  Phi. 

Soc.,  Phila.,  vol.  14,  1874. 

Massive,  without  crystalline  structure  ;  fine  granular.  Fracture  uneven. 
Brittle.  Color  lead-gray,  inclining  to  iron-black.  Luster  metallic.  Soft. 
G.  6'737.  Analysis  by  Genth  :  lead  12'76,  silver  2475,  bismuth  47'27,  zinc 
0'13,  iron  0'07,  sulphur  15'02. 

First  noticed  in  the  Treasure  Vault  mine,  Geneva  district, 
Clear  Creek  county,  from  whence  the  mineral  came  which 
was  analyzed  by  Mr.  Genth.  It  occurs  in  all  the  older  veins 
in  the  district,  finely  disseminated  through  quartz.  It  has 
never  been  noticed  in  the  newer  or  subsequently-formed  veins 
which  carry  a  large  amount  of  galena,  very  little  of  which  is 
found  in  the  bismuth-bearing  veins.  Dana's  Mineralogy 
credits  the  mineral  to  the  lied  Cloud  mine,  Boulder  county, 
where  he  says  it  "occurs  with  other  tellurium  minerals." 
The  location  is  erroneous,  as  the  mineral  has  never  been  found 
in  that  county.  It  was  named  after  J.  F.  L.  Scbirmer.  The 
schirmerite  of  Endlich  was  found  to  be  a  mixture  of  petzite 
and  some  other  minerals,  and  therefore  not  entitled  to  a  name. 
Specimens  in  compiler's  cabinet. 


Graphic  Tellurium.  Telluride  of  Gold  and  Silver.  Silli- 
man,  Am.  Jr.  Sc.,  July,  1874,  and  Clarke,  Oct.,  1877  ;  Genth,  Am.  Phi. 
Soc.,  Phila.,  1874. 

Monoclinic  ;  occurs  in  indistinct  and  minute  circular  crystals,  modified  at 
the  edges  and  angles,  and  often  grouped  in  rows,  forming  triangular  figures 
like  letters;  also  massive,  imperfectly  columnar,  granular.  Cleavage  in 
two  directions,  nearly  at  right  angles;  one  very  perfect;  Luster  metallic. 
Color  steel-gray  to  tin-white  and  brass-yellow.  Streak  like  color.  H.  l'5-2. 
G.  5'732-8'28.  Analysis  by  Genth  of  mineral  from  Red  Cloud  mine,  Gold 
Hill:  gold  24-83,  silver  13'05,  tellurium  56'31,  copper  0'23,  zinc  0'45,  iron 
3'28,  sulphur  T82,  selenium  trace,  quartz  0'32.  Analysis  of  mineral  from 
Grand  view  mine,  by  Clarke  :  tellurium  52'96,  gold  26'39,  silver  10'55, 
iron  4'45,  sulphur  5*62. 

Quite  abundant  in  crystals  and  crystalline  masses  dissem- 
inated .through  quartz,  in  the  the  Red  Cloud,  Prussian,  Cold 
Spring  and  other  veins  at  Gold  Hill;  in  the  American  and 
Grand  View  veins  at  Sunshine,  Boulder  county.  Specimens 
in  compiler's  cabinet. 


Konig,  Am.  I  hi.  Soc.,  Phila.,  1877. 
Orthorhombic;  usually  in  tabular  prisms;  often  lengthened  into  strips 
with  parallel  sides;  easily  cleavable.  Luster  submetalhc,  pearlv.  Color 
bronze-yellow,  gold-yellow,  brownish.  Powder  like  mosaic  gold.  Trans- 
lucent and  slightly  elastic  in  thin  leaves.  H.  3.  G.  3'324.  Analysis  by 
Konig  of  Colorado  mineral  ;  silica  34'68,  titanic  acid  13'58,  zirconia  2'20, 
sesquioxyd  of  iron  5'56,  alumina  0'70,  protoxyd  of  iron  26'10,  protoxyd  of 
manganese  3'48,  soda  2'54,  potassa  5'01,  water  3'54,  magnesia  0'30,  oxyd  of 
copper  0-42,  tantalic  acid  (?)  0'80. 

Beautiful  specimens  are  found  in  veins  on  Cheyenne  Moun- 
tain, in  quartz,  associated  with  arfvedsonite  and  zircon. 
Specimens  in  compiler's  collection. 


Minerals  of  Colorado.  33 

GARXBT. 

Isometric;  occurs  in  dodecahedrons,  also  in  trapezohedrons,  and  both 
forms  are  sometimes  variously  modified.  Cleavage  parallel  to  the  faces  of 
the  dodecahedron,  rather  distinct.  Also  found  massive  granular  and 
coarse  lamellar.  Color  red,  brown,  yellow,  white,  apple-green,  black; 
some  red  and  green  colors  often  bright.  Streak  white.  Lustre  vitreous — 
resinous.  Transparent — subtranslucent.  Fracture  subconchoidal,  uneven. 
H.  6.5-7.5.  G.  4'13.  Composition  varies,  silica,  alumina,  iron,  lime,  etc. 
There  are  three  prominent  varieties,  based  on  the  nature  of  the  com- 
position. (See  Spessartite  and  Almandite.} 

Red,  brown  and  black  garnets  occur  quite  frequently  in  the 
Archean.  A  reddish-brown  garnet  between  Georgetown  and 
Green  Lake,,  and  on  Saxon  Mountain.  Quite  abundant  near 
the  head  of  Fall  River,  on  Trail  Creek,  Bergen  Park,  Central 
City,  and  other  localities.  A  black  variety  in  a  vein  near 
Hoosier  Pass.  Small  garnets,  probably  almandite,  of  beauti- 
ful color,  are  found  in  quantities  in  the  gold  washings  at  Fair- 
play  and  Breckenridge;  impure  alnwndite  near  Salida  (p.  48). 
Spessartite  at  Nathrop  in  rhyolite,  and  in  the  Grand  Canon 
of  the  Arkansas  (p.  j6). 

UMONITB.      Brown  Iron  Ore.     Brown  Ochre. 

Usually  in  stalactitic  and  botryoidal  or  mammilary  forms,  having  a  fibrous 
or  subfibrous  structure;  also  concretionary,  massive,  and  occasionally 
earthy.  Lustre  silky,  often  submetallic;  sometimes  dull  and  earthy. 
Color  of  surface  of  fracture  various  shades  of  brown,  commonly  dark,  and 
none  bright ;  sometimes  with  a  nearly  black  varnish-like  exterior  ;  when 
earthy,  brownish-yellow,  ochre-yellow.  Streak  yellowish-brown.  H.  5 — 
5'5.  G.  3'6-4.  Comp.,  sesquioxyd  of  iron  85'6,  water  14*4. 

A  brown  hematite  of  excellent  quality  is  found  in  the  Hot 
Springs  mine,  Saguache  County, which  has  been  quite  exten- 
sively mined.  At  Villa  Grove,  in  the  same  county.  A  bog 
ore  is  found  near  Crested  Butte.  Analyses  of  ore  from  these 
localities  have  been  made  at  the  State  School  of  mines 

Hot  Villa  Crested 

Springs.  Grove.  Butte. 

Silica  9-33  10'19  2'50 

Water lO'ol  13'57  23'97 

Alumina 3'43  3'60  0'28 

Oxide  of  Manganese 0'35 

Lime 0-83  0'45  0'22 

Magnesia 0'06  0'22  0'12 

Peroxide  of  Iron 75'23  70'39  72'47 

Phosphoric  acid 0'071  0'92  0'333 

Sulphur  0-019  0'18 


99-830          99-62  99'893 

"This  ore  is  a  chemical  curiosity,"  says  Prof.  Chauvenet,  of 
the  State  School  of  Mines,  in  speaking  of  the  hematite'  from 
Crested  Butte.  "containing  at  once  figures  on  certain  constit- 
uents which  are  phenomenal  for  highness  and  lowness  respect- 
ively. After  burning  this  ore  would  be  enriched  to  nearly 


34  Minerals  of  Colorado. 

sixty-seven  per  cent  of  metallic  iron  by  the  loss  of  water  and 
organic  matter."  The  ore  is  said  to  approximate  to  half  a 
mile  square  in  extent,  with  an  uncertain  depth. 

Limonite  exists  in  numerous  other  localities  —  between 
South  Boulder  and  Coal  Creeks;  on  Bear  Creek;  in  South 
Park;  at  Trinided;  beautiful  specimens  on  Little  Thompson, 
at  the  foot  of  the  mountains. 


Carbonate  of  Soda. 
Monoclinic.      Vitreous   to    earthy.     White,   sometimes   gray   or  yellow. 
Taste  alkaline.     H.  1-1-5.     G.  T423.     Comp.,   carbonic  acid  26'7,  soda 
18'8,  water  54'5. 

About  twelve  miles  south-west  of  Denver,  between  Turkey 
and  Bear  Creeks,  are  four  small  lakes  containing  in  solution 
a  large  amount  of  soda. 

MAGNETITE.     Magnetic  Iron  Ore.     Octahedral  Iron  Ore. 

Isometric;  octahedrons  and  rhombic  dodecahedrons:  cleavage  octahedral. 
Massive,  and  in  particles  of  various  sizes,  sometimes  impalpable.  Lustre 
metallic  —  submetallic.  Color  iron-blacK.  Streak  black.  Fracture  sub- 
conchoidal,  shining.  Brittle.  Strongly  magnetic,  sometimes  possessing 
polarity.  H'  5*5-6'5.  G.  4'9-5'2.  Comp.,  oxygen  27'6,  iron  72'4. 

The  Calumet  mine,  ChafFee  County,  is  the  only  iron  mine 
in  the  State  producing  magnetite,  upon  which  the  steel 
works  at  Pueblo  are  largely  dependent.  The  mine  has  been 
opened  to  a  depth  of  about  300  feet,  and  to  a  rmich  greater 
distance  horizontally.  Analysis  by  School  of  Mines,  Golden: 

Silica  7'04,  alumina  T90,  peroxyd  of  iron  56'76,  protoxyd  of  iron  26'88,  bisul- 
phide of  iron  1'14,  lime  1'59,  magnesia  T70,  phosphoric  acid  0*16,  titanic  acid 
trace. 

At  Caribou  a  seven-foot  vein  of  very  pure  ore.  On  Elk 
Creek. 

HEMATITE.     Specular  Iron.     Red  Ochre. 

Rhombohedral  ;  in  complex  modifications  of  a  rhombohedron  ;  crystals 
occasionally  thin  tabular;  also  occurs  granular,  botryoidal,  and  stalactitic 
shapes;  lamellar,  the  laminae  variously  bent,  and  thick  or  thin.  Lustre 
metallic  and  occasionally  splendent;  sometimes  earthy.  Color  dark  steel- 
gray  or  iron-black  ;  in  very  thin  particles  blood-red  by  transmtited  light  ; 
when  earthy,  red.  Streak  cherry-red  or  reddish-brown.  Sometimes  at- 
tractable by  the  magnet,  and  occasionally  even  magnetic-polar.  H.  5'5- 
6'5.  G.  4'5-5'3.  Comp.,  oxygen  30,  iron  70. 

An  impure  hematite  occurs  in  the  Hawkins  bank,  ChafFee 
County.  The  following  analysis  of  the  ore  was  made  at  the 
State  School  of  mines: 

Silica  22-33,  water  3'10,  alumina  3.06,  lime  0'08,  magnesia  0'06,  peroxide  of 
iron  70'40,  phosphoric  acid  0'614,  sulphur  0'056. 

Occurs  as  an  ochre  near  Florissant,  with  gothite,  microcline, 
quartz,  fluorite,  etc.  A  micaceous  variety  quite  abundant  on 
Left  Hand  Breek,  Ward  District,  Boulder  County,  and  is 
found  in  small  quantities  in  numerous  localities. 


Minerals  of  Colorado*  35 

MUSCOVITE.     Common  Mica.     Potash  Mica.     Oblique  Mica. 

Orthorhombic  ;  occurs  in  oblique  rhombic  prisms  with  basal  cleavage  ; 
usually  in  thinly  foliated  masses  ;  folia  often  aggregated  in  stellate,  or 
globular  forms.  Lustre  more  or  less  pearly.  Color  white,  gray,  brown, 
hair-brown,  pale  green,  yiolet,  yellow,  dark  olive-green,  rarely  rose-red  ; 
often  different  for  transmitted  and  reflected  light,  and  different  also  in 
vertical  and  transverse  directions.  Streak  uncolored.  Transparent  to 
translucent.  Thin  lamina  flexible,  elastic,  tough.  Double  refracting. 
H.  2-2.5  G.  2.75-3.1.  Comp.,  silica  46,  alumina  37,  potash  9,  peroxyd  of 
iron  4,  fluoric  acid  1,  water  2. 

A  constituent  of  much,  of  the  Archean  rocks,  and  occasion- 
ally found  in  quite  large  masses.  Several  attempts  have  been 
made  to  develop  deposits  in  Jefferson  and  Clear  Creek  Coun- 
ties, but  without  success.  Near  Canon  City  quite  a  large  de- 
posit which  has  been  worked  with  limited  success. 


Magnesia-Mica.  Hexagonal  Mica. 
Hexagonal  ;  prisms  usually  tabular,  with  perfect  basal  cleavage.  Often  in 
disseminated  scales,  sometimes  in  massive  aggregations  or  clsavable  scales. 
Lustre  splendent,  and  more  or  less  pearly  on  a  cleavage  surface,  and  some- 
times submetallic  when  black  ;  lateral  surface  vitreous  when  smooth  and 
shining.  Colors  usually  green  to  black,  often  deep  black  in  thick  crystals; 
thin  laminae  green,  blood-red,  or  brown  by  transmitted  light  ;  rarely 
white.  Streak  uncolored.  Transparent  to  opaque.  Tough  and  elastic. 
H.  2.5-3.  G.  2.7-3.1.  Comp.,  varies,  silica  39,  alumina  15,  peroxyd  of 
iron  8,  magnesia  24,  soda  1,  potash  9,  water  1,  flluorine,  chlorine,  etc. 

The  mica  of  the  Archean  rocks  is  mainly  biotite.  It  also 
occurs  in  the  dike  rocks. 

BISMUXIXE.     Carbonate  of  Bismuth. 

In  implanted  acicular  crystallizations  (pseudomorphs);  also  incrusting  or 
amorphous  ;  pulverulent.  Lustre  vitreous  when  pure  ;  sometimes  dull. 
Color  white,  mountain-green,  and  dirty  siskin-green;  occasionally  straw- 
yellow  and  yellowish-gray.  Streak  greenish-gray  to  colorless.  Subtrans- 
lucent—  opaque.  H.  4-4.5.  G.  6.86-6.909. 

Near  Cummens  City,  North  Park.  In  the  mountains  west 
of  Fort  Collins,  where  a  number  of  veins  have  been  prospect- 
ed. In  the  L,as  Animas  mine,  Gold  Hill.  In  white  quartz 
on  Guy  Hill,  Jefferson  County,  with  bismuthinite. 


Sulphuret  of  Manganese. 
Isometric;  in  cubes  and  octahedrons.  Cleavage,  cubic  perfect,  crystals 
sometimes  cruciform,  made  of  five  combined  octahedrons.  Usually  mass- 
ive. Lustre  submetallic.  Color  iron-black,  tarnished  brown  on  exposure. 
Streak  green.  H.  3'5-4.  G.  3'95-4'04.  Comp.,  sulphur  36'7,  manganese 
63-3. 

A  '  'pocket'  '  of  this  mineral  was  encountered  in  sinking  the 
shaft  on  the  Queen  of  the  West  mine,  Summit  County,  about 
300  feet  from  the  surface.  Occasionally  crystals  are  met  with. 
The  only  immediate  associate  mineral  is  rhodochrosite,  al- 
though the  mine  carries  galena,  pyrite  and  argentite.  The 
alabandite  carries  about  30  ounces  of  silver  to  the  ton.  This 
is  the  first  published  instance  of  its  occurrence  in  America. 


36  Minerals  of  Colorado. 

SPESSAR.XITK.      Manganese- Alumina  Garnet.      W.  Cross,  U.  S.  Geo. 

Sur.,  Am.  Jr.  Sc.,  June,  1866. 

Isometric ;  occurs  in  dodecahedrons,  also  in  trapezohedrons,  and  both 
forms  are  sometimes  variously  modified.  Cleavage  parallel  to  the  faces  of 
the  dodecahedron,  rather  distinct.  Also  found  massive  granular  and 
coarse  lamellar.  Color  dark  hyacinth-red,  sometimes  with  a  shade  of 
violet,  to  brownish-red.  Streak  white.  Lustre  vitreous — resinous.  Trans- 
parent— subtranslucent.  Fracture  subconchoidal,  uneven.  H.  6.5-7.5. 
G.  4'13.  Analysis  of  Nathrop  mineral  by  L.  G.  Eakins:  silica  35.66, 
alumina  18.55,  sesquioxyd  of  iron  .32,  protoxyd  of  iron  14.25,  protoxyd  of 
manganese  29.48,  lime  1.15,  potassa  .27,  soda  .21,  water  .44. 

Occurs  at  Nathrop  in  lithophyses  of  rhyolite,  associated 
with  topaz.  In  a  similar  rock  in  the  Grand  Canon  of  the  Ar- 
kansas. 

EPIDOXE. 

Monoclinic;  in  right  rhomboidal  prisms,  more  or  less  modified,  often 
with  six  or  more  sides ;  also  fibrous,  divergent  or  parallel ;  also  granular, 
particles  of  various  sizes,  sometimes  fine  granular  and  forming  rock 
masses.  Lustre  vitreous,  inclining  to  pearly  or  resinous.  Color  pistachio- 
green  to  brownish-green,  greenish-black  to  black  ;  sometimes  clear  red  and 
yellow;  also  gray  and  grayish-white.  Subtransparent— opaque ;  gener- 
ally subtranslucent.  Fracture  uneven.  Brittle.  H.  6-7.  G.  3.25-3.5. 
Comp.,  silica  37.0,  alumina  26.6,  lime  20.0,  protoxyd  of  manganese  0.6, 
water  1.8. 
Of  frequent  occurrence  in  the  Archian,  usually  massive. 

Very  good  crystals  have  been  found  on  Floyd  Hill  and  on 

Bear  Creek. 

MALACHITE.     Green  Carbonate  of  Copper. 

Monoclinic;  rarely  occurs  crystallized ;  usually  massive  or  incrustating, 
with  surface  tuberose,  botryoidal  or  stalactitic,  and  structure  divergent; 
often  delicately  compact  fibrous,  and  banded  in  color;  frequently  granular 
or  earthy.  Lustre  of  crystals  adamantine,  inclining  to  vitreous ;  fibrous 
varieties  more  or  less  silky ;  often  dull  and  earthy.  Color  bright  green. 
Streak  pale  green.  Translucent,  subtranslucent,  opaque.  Fracture  sub- 
conchoidal, uneven.  H.  3.5.7—4.  G.  3.7 — 4.01.  Comp.,  carbonic  acid 
19.9,  protoxyd  of  copper  71.9,  water  8.2. 

Of  general  occurrence  throughout  the  State  near  the  sur- 
face of  mineral  veins,  but  in  small  quantities,  and  usually  as 
incrustations. 

CER.USSIXE.     Carbonate  of  Lead.     White  Lead  Ore. 

Orthorhombic ;  crystals  usually  thin,  broad  and  brittle;  sometimes  stout; 
rarely  fibrous;  often  granular,  massive  and  compact;  sometimes  stalactitic. 
Lustre  adamantine,  inclining  to  vitreous  or  resinous ;  sometimes  pearly; 
frequently  submetallic  if  the  colors  are  dark,  or  from  a  superficial  change. 
Color  white,  gray,  grayish-black,  yellowish,  sometimes  tinged  blue  or 
green  by  some  of  the  salts  of  copper.  Streak  uncolored.  Transparent — 
subtranslucent.  Fracture  conchoidal.  Very  brittle.  H.  3-3'5.  G.  6.465- 
6.480.  Comp.,  carbonic  acid  16.5,  oxyd  of  lead  83.5. 

Abundant  at  Leadville,  and  occasionally  in  fine  crystalline 
masses.  Also  abundant  in  numerous  localities  south  of  Lead- 
ville. Occurs  in  small  quantities  at  the  surface  of  silver 
veins  in  the  Archian. 


Minerals  of  Colorado.  87 

TIXAIVI'TE.     Sphene. 

Monoclinic;  in  very  oblique  rhombic  prisms;  crystals  usually  thin,  with 
sharp  edges.  Cleavage  in  one  direction  sometimes  perfect.  Occasionally 
massive.  Color  grayish-brown,  gray,  brown  or  black  ;  sometimes  yellow 
or  green  ;  streak  uncolored.  Lustre  adamantine  to  resinous.  Transparent 
to  opaque.  Brittle.  H.  5-5'5.  G.  3'4-3'56.  Comp.,  silica  30'5,  titanic 
acid  41-3,  lime  28'2. 

Occurs  in  crystals  in  the  augitic  rock  on  Italian  Mountain, 
Gunnison  County. 

CHRYSOWTE.     Olivene.    Peridot. 

Orthorhombic;  in  right  rectangular  prisms,  having  perfect  cleavage  par- 
allel with  the  smaller  lateral  plane  ;  usually  in  imbedded  grains,  of  an  ol- 
ive-green color,  looking  like  green  bottle  glass  ;  also  yellowish-green. 
Transparent  to  translucent.  Looks  much  like  glass  in  the  fracture,  except 
in  the  direction  of  the  cleavage.  H.  6-7.  G.  3'33-3'5.  '  Comp.,  silica  38'5, 
magnesia  48'4,  protoxyd  of  iron  1T2,  oxyd  of  manganese  0'3,  alumina  0'2. 

Occurs  in  the  basalt  of  Bastion  Peak. 

PYROMOR.PHITE.     Green  Lead  Ore.     Phosphate  of  Lead. 

Hexagonal  ;  occurs  in  six-sided  prisms,  usually  modified  on  the  edges,  and 
frequently  striated  horizontally  ;  often  globular,  reniform,  and  botryoidal, 
with  a  subcolumnar  structure;  also  fibrous  and  granular.  Lustre  resinous. 
Color  green,  yellow  and  brown  of  different  shades;  sometimes  wax-yellow 
and  fine  orange-yellow  ;  also  greenish-white  or  milk-white.  Streak  white, 
sometimes  yellowish.  Subtransparent-stibtranslueent.  Brittle.  II.  3'5-4. 
G.  6'5-7'l.  Comp.,  phosphoric  acid  15*7,  oxyd  of  lead  74'1,  chlorine  2'6, 
lead  7-6 

Sparingly  in  the  mines  at  L/eadville,  and  in  the  Astor  and 
Freeland  mines,  Clear  Creek  County. 


Hexagonal  ;  occurs  in  six  and  twelve  sided  prisms,  with 
plane  or  modified  summits.  Prismatic  cleavage,  distinct.  Also  massive, 
compact,  and  thin  columnar.  Lustre  vitreous,  greasy;  a  little  opalescent 
in  some  varieties.  Colorless,  white  or  yellowish;  also  when  massive, 
dark  green,  greenish  or  bluish-gray,  brownish  and  brick-red.  Transpa- 
rent-opaque. Fracture  subconchoidal.  H.  5*5-6.  G.  2'5-2'65.  Comp., 
silica  44-2,  glucina  337,  soda  16'9,  potash  5'2. 

In  the  basalt  of  Bastion  Peak  and  elsewhere  in  the  Elkhead 
Mountains. 

AXIVABKRGITE.  Nickel  Ochre.  Nickel  Green.  Arseniate  of  Nickel. 
Monoclinic;  in  capillary  crystals;  also  massive  and  disseminated.  Color 
fine  apple-green,  Streak  greenish-white.  Fracture  uneven,  or  earthy. 
Soft.  Comp.,  arsenic  acid  38'6,  oxyd  of  nickel  37'2,  water  24'2. 

Occurs  as  an  alteration  product  of  niccolite  in  the  Gem 
mine,  on  Pine  Creek,  Fremont  County. 

CHAI,COCIT'E.     Vitreous  Copper  Ore.     Copper  Glance. 

Orthorhombic  ;  in  six-sided  prisms,  variously  modified  ;  also  massive, 
structure  granular,  or  compact  and  impalpable.  Lustre  metallic.  Color 
and  streak  blackish  lead-gray  ;  often  tarnished  blue  or  green.  Fracture 
conchoidal.  Streak  sometimes  shining.  H.  2'5-3.  G.  5'5-5'8.  Comp. 
sulphur  20'2,  copper  79'8. 

Abundant  in  copper  veins  near  Canon  City;  also  in  Bergen 
Park  and  on  Bear  Creek,  Jefferson  County. 


38  Minerals  of  Colorado. 

XAOYAGIXE.     Black  Tellurium.     Foliated  Tellurium. 

Tetragonal ;  occurs  in  small  six-sided  tables  with  a  basal  cleavage;  also 
massive-granular,  but  generally  foliated.  Lustre  metallic,  splendent. 
Streak  and  color  blackish  lead-gray.  Flexible  in  thin  laminse.  H.  1-1*5. 
G.  G-85-7'2.  Comp.,  tellurium  15  to  32,  sulphur  3  to  9,  lead  50  to  60,  gold 
5  to  12. 

Occasionally  met  with  in  the  tellurium  mines  of  Boulder 
County. 

GAUENI'FE.     Galena.     Sulphuret  of  Lead. 

Isometric;  occurs  crystallized  in  the  cube,  octahedron,  and  in  numerous 
combinations  of  these,  with  planes  of  other  figures;  also  in  amorphous 
masses  with  a  lamellar  structure;  frequently  granular  ;  occasionally  fibrous. 
Cleavage  cubic.  Lustre  metallic.  Color  and  streak  pure  lead-gray.  Sur- 
face of  crystals  occasionally  tarnished.  Sectile.  Easily  pulverized,  and 
easily  frangible.  H.  2-5-2'75.  G.  4'25-7'7:  Comp.,  sulphur  13*4,  lead  86'6. 

Of  general  occurrence  throughout  the  mining  regions,  and 
usually  containing  a  profitable  per  cent  of  silver.  Good  crys- 
tals only  occasionally  met  with.  Specially  fine  clusters  have 
been  taken  from  the  Dunderberg  and  Terrible  mines,  George- 
town, and  from  the  Running,  Calhoun  and  Glennan  mines, 
in  Gilpin  County. 

DECMENITE. 

Occurs  massive,  botryoidal,  nodular,  stalactitic ;  sometimes  traces  of  a  col- 
umnar structure.  Lustre  of  fresh  fracture  greasy.  Color  fine  deep  red  to 
yellowish-red  and  brownish-red  ;  also  leather-yellow.  Streak  orange-yel- 
low to  pale  yellow.  H.  3-4.  G.  5'6-5'81.  Comp.,  vanadic  acid  47,  oxyd 
of  lead  53. 

Occurs  in  the  Evening  Star  mine,  L/eadville,  of  dark  red  to 
yellow  color. 

WIXHER.ITE.     Carbonate  of  Baryta. 

Orthorhombic ;  in  modified  rhombic  prisms  and  in  six-sided  prisms  ter- 
minated with  pyramids;  also  in  globular,  tuberose  and  botryoidal  forms  ; 
structure  columnar,  granular  or  amorphous.  Lustre  vitreous,  inclining  to 
resinous,  on  surface  of  fracture.  Color  white,  often  yellowish  or  grayish. 
Streak  white.  Subtransparent — translucent.  Fracture  uneven.  Brittle. 
H.  3-3-75.  G.  4'29-4'35.  Comp.,  carbonic  acid  22'3,  baryta  777. 

In  white  masses  on  Cotton  Creek,  San  Luis  Park.  This 
mineral  is  poisonous. 

BAR.ITE.     Heavy  Spar.     Sulphate  of  Baryta. 

Orthorhombic;  in  modified  rhombic  and  rectangular  prisms;  crystals 
usually  tabular;  also  columnar,  fibrous,  granular  and  compact.  Lustre 
vitreous,  inclining  to  resinous,  sometimes  pearly.  Streak  white.  Color 
white,  yellow,  gray,  blue,  red,  brown.  Transparent,  translucent,  opaque. 
Sometimes  fetid  when  rubbed.  H.  2'5-3'5.  G.  4'3-4'8.  Comp.,  sulphuric 
acid  34,  baryta  66. 

Of  frequent  occurrence  in  the  mines,  both  crystallized  and 
massive.  Extensive  beds  on  Vasquez  River.  Fine  single 
crystals  with  calcite  on  Apishapa  Creek.  Beautiful  clusters 
of  crystals  in  the  Seven-Thirty  mine,  Georgetown.  Barite  is 
used  as  a  paint,  and  in  adulterating  white  lead. 


Minerals  of  Colorado.  39 

CAL,CIXE.     Calcareous  Spar.     Carbonate  of  Lime. 

Rhombohedral  ;  occurs  crystallized  in  upwards  of  800  varieties  of  form. 
The  primary  form  is  an  obtuse  rhombohedron,  which  may  readily  be  ob- 
tained by  cleavage.  Also  fibrous,  both  coarse  and  fine  ;  sometimes  lamel- 
lar; often  granular;  also  stalactitic.  Lustre  vitreous  —  subvitreous  —  earthy. 
Color  white  or  colorless,  also  various  shades  of  red,  green,  gray,  blue,  yel- 
low, violet  ;  brown  and  black  when  impure.  Streak  white  or  grayish. 
Transparent—  opaque.  Double  refraction  strong.  G  2'508-2'776.  H.  2'6- 
3'5.  Corup.,  carbonic  acid  44,  lime  56. 

Large  white  masses  on  Bear  Creek,  five  miles  above  Mor- 
rison, in  granite.  On  Box  Elder  Creek,  Laramie  County,  in 
aggregations  of  crystals,  and  in  many  other  localities  along 
the  base  of  the  mountains. 

ICELAKD    SPAR. 

Transparent  variety  of  calcite.     Double  refracting  in  a  high  degree. 

Near  Canon  City,  on  Beaver  Creek;  on  the  Greenhorn  and 
Apishapa;  in  the  lava  of  the  Table  Mountains,  Golden. 

ARGENTINE. 

A  foliated,  white  pearly  calcite. 

On  Chalk  Mountains,  in  veins  sometimes  from  two  to  three 
feet  thick. 

MARBLE.     Granular  Limestone. 

Calcite  having  a  texture  like  loaf  sugar  when  broken.  The  texture  varies 
from  coarse  to  fine  granular,  and  the  latter  passes  by  imperceptible  shades 
into  compact  limestone.  The  colors  are  various  and  usually  clouded. 

A  large  vein  of  black  white  and  gray  marble  in  South 
Park.  Brownish-gray  marble  near  Canon  City.  Hard  com- 
pact limestone  frequently  makes  a  fine  stone  when  polished. 
A  black  variety  veined  with  white  occurs  on  Cotton  Creek, 
San  Luis  Park.  Breccia  marble  near  Boulder.  Shell  marble 
near  Colorado  Springs.  Encrinal  marble  at  Sangre  de 
Christo  Pass. 

DESCLOIZIXB. 

Orthorhornbic.  Lustre  bright.  Color  black  to  olive-brown  ;  smallest 
crystals  olive-green,  with  a  chatoyant  bronze  lustre  ;  by  transmitted  light 
along  the  edges  light  brown,  inclining  to  red;  on  a  surface  of  fracture, 
colors  zoned  with  straw-yellow,  reddish-brown  and  black;  nearly  clear  at 
middle  and  darkest  at  extremities  of  crystal.  H.  3*5.  G.  5*839.  Comp., 
vanadic  acid  29'3,  oxyd  of  lead  70'7. 

Sparingly  in  the  Evening  Star  and  other  mines,  Leadville. 


Porcelain  Clay. 

Orthorhornbic;  occurs  in  rhombic,  rhomboidal,  or  hexagonal  scales  or 
plates;  sometimes  in  fan-shaped  aggregations;  usually  constituting  a  clay- 
like  mass,  either  compact,  friable  or  mealy.  Lustre  of  plates  pearly  ;  of 
mass,  pearly  to  dull  earthy.  Color  white,  grayish-white,  yellowish,  some- 
times brownish,  bluish  or  reddish.  Scales  flexible.  Usually  unctious  and 
plastic.  H.  1-2-5.  G.  2'4-2'63.  Comp.,  silica  46,  alumina  40,  water  14. 

Occurs  as  the  result  of  the  decomposition  of  the  feldspars  of 
granitic  rocks  and  porphyries  throughout  the  state.  Kaolin 
is  used  in  making  porcelain  and  china  ware. 


40  Minerals  of  Colorado. 

VESUVIA1VITE.     Idocrase. 

Tetragonal ;  crytals  usually  in  modified  square  prisms ;  also  found  massive. 
Color  brown  to  green,  the  latter  frequently  bright  and  clear ;  occasionally 
sulphur-yellow,  and  also  pale  blue.  Lustre  vitreous,  often  inclining  to 
resinous.  Streak  white.  Subtransparent  to  nearly  opaque.  H.  6'5.  G. 
3'34.  Comp.,  silica  38'4,  alumina  23'7,  protoxyd  of  iron  4'0,  lime  29'7, 
magnesia  and  protoxyd  of  manganese  5'2. 

Occurs  in  beautiful  yellowish-green  crystals  on  Italian  Mt. , 
Gunnison  County,  which  are  said  to  be  the  finest  found  in  the 
United  States.  In  brown  crystals  on  Bear  Creek. 

AZURITE.     Chessy  Copper.     Blue  Carbonate  of  Copper. 

Monoclinic;  in  modified  oblique  rhombic  prisms,  the  crystals  rather  short 
and  stout;  lateral  cleavage  perfect.  Also  massive,  incrusting  and  earthy. 
Lustre  vitreous,  almost  adamantine.  Color  various  shades  of  azure-blue, 
passing  into  berlin-blue.  Streak  blue,  lighter  than  the  color.  Transpa- 
rent-subtranslucent.  Fracture  conchoidrl.  Brittle.  H.  3'5-52'5.  G. 
3'5-3'831.  Comp.,  carbonic  acid  25'6,  oxyd  of  copper  69'2,  water  5'2. 

Occurs  as  on  incrustation  on  the  surface  ores  of  many  of 
the  mines  throughout  the  state. 

AR.SENOPYR.ITE.     Mispickel.    Arsenical  Pyrites. 

Orthorhombic ;  crystallizes  in  right  rhombic  prisms,  parallel  to  whose 
planes  it  may  be  cleaved  ;  also  occurs  columnar,  straight  and  divergent; 
granular  or*  compact.  Lustre  metallic.  Color  silver-white,  inclining  to 
steel-gray.  Streak  dark  grayish-black.  Fracture  uneven.  Brittle.  H. 
5-5-6.  G.  G'0-6-4.  Comp.,  arsenic  46'0,  sulphur  19'6,  iron  44'4.  Part  of 
the  iron  sometimes  replaced  by  cobalt. 

Occurs  sparingly  in  some  of  the  mines  of  Gilpin  and  Clear 
Creek  Counties. 

CUPRITE.     Eed  Oxyd  of  Copper. 

Isometric;  in  regular  octahedrons  and  modified  forms  of  the  same.  Cleav- 
age octahedral.  Also  massive,  granular ;  sometimes  earthy.  Lustre  ada- 
mantine or  submetallic  to  earthy.  Color  red,  of  various  shades,  particu- 
larly cochineal-red  ;  occasionally  crimson-red  by  transmitted  light.  Streak 
brownish-red,  shining.  Subtransparent-subtranslucent.  Fracture  conch - 
oidal,  uneven.  Brittle.  H.  3'5-4.  G.  5'85-6"15.  Comp.,  oxygen  11"2, 
copper  88*8. 

In  crystals,  Sacramento  Gulch,  and  in  Sweet  Home  mine, 
Buckskin.  Malachite  lode,  Bear  Creek.  Massive  at  Poncha 
Springs. 

OPAL. 

Massive,  amorphous ;  sometimes  small  reniform,  stalictitic,  or  large  tube- 
rose. Lustre  vitreous,  frequently  subvitreous ;  often  inclining  to  resinous, 
and  sometimes  to  pearly.  Color  white,  yellow,  red,  brown,  green,  gray, 
generally  pale;  sometimes  a  rich  play  of  colors,  or  different  colors  by  re- 
fracted or  reflected  light.  Transparent  to  nearly  opaque.  H.  5'5-6'5.  G. 
l'9-2:3.  Comp.,  silica,  same  as  quartz,  with  a  little  water. 

A  milk-white  opal  occurs  in  the  decomposition  product  of 
the  lava  on  Buffalo  Peaks,  in  the  Mosquito  Range.  A  yel- 
lowish, slightly  translucent  opal  is  quite  abundant  six  miles 
south  of  the  salt  works,  in  South  Park,  associated  with  jasper 
and  chalcedony. 


Minerals  of  Colorado.  41 

FIRE  OPAL. 

A  variety  of  opal  presenting  hyacinth-red  to  honey-yellow  and  bluish  col- 
ors, with  fire-like  reflections,  somewhat  irised  on  turning. 

A  bluish  transparent  opal,  with  yellowish  reflections,  oc- 
curs in  a  felsitic  rick  near  Idaho  Springs,  which  has  been 
used  to  considerable  extent  in  jewelry. 

MYAI.1XE.     Muller's  Glass. 

An  opal  usually  clear  as  glass  and  colorless,  constituting  globular  concre- 
tions, and  also  crusts  with  a  globular,  reniforrn,  botryoidal,  or  stalactitic 
surface. 

Occurs  near  the  head  of  Cache  la  Poudre  Creek,  and  on  the 
La  Garita,  in  pearly  crusts,  on  lava. 

WOOD    OPAL. 

Wood  petrified  by  opal  of  various  shades  of  color. 

Abundant  along  the  sources  of  Cherry,. Kiowa  and  Bijou 
Creeks,  at  Happy  Canon,  and  in  Middle  Park,  much  of  which 
is  agate-like  in  structure,  and  of  a  diversity  of  colors. 

BKRAL. 

Hexagonal ;  usually  in  long,  stout  six-sided  prisms,  without  regular  ter- 
minations; occasionally  coarse  columnar.  Lustre  vitreous,  sometimes  res- 
inous. Color  bright  green  (when  it  is  known  as  emerald],  pale  green,  pass- 
ing into  light  blue  (aquamarine], yellow  and  white.  Transparent-subtrans- 
lucent.  H.  7'5-8.  G.  2'63-2  76.  Comp.,  silica  66'8,  alumina  19'1,  glu- 
cina  14'1. 

Beryls  of  enormous  size,  but  nearly  opaque  and  of  inferior 
color,  in  white  quartz,  on  Bear  Creek.  Small  crystals  of  light 
green  color  in  the  Floyd  Hill  region;  also  on  the  Platte  River, 
at  the  edge  of  South  Park.  Colorless  and  light  green  trans- 
parent crystals  on  Mt.  Antero,  Chaffee  County. 

AQUAMARINE. 

Beryls  of  a  sea-green  or  pale  bluish-green  tint. 

Beautiful  transparent  crystals,  of  bluish-green  color,  occur 
on  Mt.  Antero,  ChafFee  County.  Rarely  on  Bear  Creek. 

GOXMITE.     Brown  Iron-Stone 

Orthorhombic;  in  prisms  longitudinally  striated,  and  often  flattened  into 
scales  or  tables  parallel  to  the  shorter  diagonal.  Cleavage  very  perfect. 
Also  fibrous,  foliated,  in  scales,  massive,  stalactitic.  Lustre  imperfect  ad- 
amantine. Color  yellowish,  reddish,  and  blackish  brown.  Often  blood- 
red  by  transmitted  light.  Streak  browish-yellow,  ochre-yellow.  H.  5-5'5. 
G.  4'6-4  4  Comp.,  sesquioxyd  of  iron  89'9,  water  lO'l. 

Abundant  in  the  Pike's  Peak  region,  in  cavities  in  granite, 
associated  with  amazonstone,  smoky  quartz,  fluor  spar,  etc. 

BASTNASITE.     Allen  &  Comstock,  Am.  Jr.  Sc.,  May,  1880. 

Hexagonal ;  occurs  in  six-sided  prisms.  Color  reddish-brown.  Lustre 
vitreous  to  resinous.  H.  4-4'5.  G.  5'18-5'20.  Analysis  of  Colorado  min- 
eral by  Allen  &  Comstock  :  oxide  of  cerium  40'88,  oxide  of  lanthanum 
and  didymium  34'95,  carbonic  acid  20'09,  fluorine  (by  difference)  4'08. 

Occurs  as  an  alteration  product  of  tysonite  west  of  Chey- 
enne Mountain,  El  Paso  County. 


42  Minerals  of  Colorado. 

PTII^OUTE.     (new.)     W.  Cross,  Am.  Jr.  Sc.,  Aug.,  1886. 

Occurs  in  white  tufts  of  short  hair-like  needles.  Analysis  by  Eakins  :  sil- 
ica 70-35,  alumina  1T90,  lime  3'87,  potassa  2'83,  soda  0'77,  water  10'16. 

Occurs  as  tufts  of  short  hair-like  needles  in  augite-andesite. 
on  the  north  slope  of  Green  Mountain,  Jefferson  County. 

ARAQOXITB. 

Orthorhombic  ;  primary  form  a  right  rhombic  prism  ;  occurs  in  hexagonal 
prisms,  very  frequently  in  twin  crystals,  also  in  globular,  reniform,  den- 
dritic, and  coralloidal  shapes;  sometimes  fibrous  and  in  compact  masses. 
Color  generally  white,  but  sometimes  tinged  yellow,  blue  and  green.  Lus- 
tre vitreous,  inclining  to  resinous  on  fractured  surfaces.  Translucent  to 
transparent.  Fracture  subconchoidal.  H.  3'5-4.  G.  2'031.  Cornp.,  car- 
bonic acid  44,  lime  56. 

Coralloidal  and  in  small  masses  in  a  number  of  lodes  on 
L,eavenworth  Mountain,  Georgetown.  Near  Golden.  One 
mile  below  Idaho  Springs  is  a  variety  very  similar  to  the  cel- 
ebrated gibralter  rock,  of  Spain.  In  South  Park,  two 
miles  south-west  of  the  Salt  Works,  in  coarsely  radiated  and 
columnar  masses.  On  Willow  Creek,  San  Luis  Valley,  a 
vein  about  30  feet  wide,  in  basalt,  portions  of  which  exhibit 
a  botryoidal  structure.  Coralloidal  at  Loma.  Six  miles  be- 
low Del  Norte,  on  the  Rio  Grande,  a  large  deposit. 


Chlorobromid  of  Silver. 
Isometric;  occurs  in  cubes  and  cubo-octahedrons  ;  also  massive,  sometimes 
stalactitic.  Lustre  resinous  and  somewhat  adamantine.  Color  grayish- 
green  and  asparagus-green  to  pistachio  or  yellowish-green,  and  yellow, 
often  dark  ;  becoming  darker  externally  on  exposure.  H.  1-1'5.  G.  5*31- 
5*43.  Comp.,  varies,  silver  61  to  71,  bromine  7  to  33,  chlorine  5  to  20. 

Sparingly  in  the  mines  of  L/eadville. 

XYSONITE.     (new.)     Am.  Jr.  Sc.,  May,  1880,  June,  1884. 

Hexagonal;  occurs  in  prisms  with  basal  cleavage.  Color  pale  wax-yellow. 
Streak  nearly  white.  Lustre  vitreous  to  resinous.  H.  4'5-5.  G.  6'14. 
Analysis  by  Allen  &  Com  stock  :  cerium  40'16,  lanthanum  and  didymium 
30-29,  fluorine  29'55. 

Occurs  near  Pike's  Peak,  associated  with  bastnasite,  both 
minerals  being  frequently  found  in  the  same  crystal,  the  cen- 
tral portion  of  the  crystal  being  composed  of  tysonite.  Spec- 
imens have  been  found  weighing  several  pounds.  Named 
after  S.  T.  Tyson,  a  metallurgist  of  Colorado. 

PYR.IXE.     Iron  Pyrites.     Bisulphuret  of  Iron. 

Isometric;  occurs  in  cubes,  simple  and  modified;  pentagonal  dodecahe- 
drons and  octahedrons;  crystals  frequently  forming  aggregations;  also 
massive  and  in  imitative  shapes.  Color  bronze-yellow.  Lustre  metallic, 
splendent.  Brittle.  H.  6-6'5.  G.4'8-5'1.  Comp.,  iron  467,  sulphur  53'3. 

Abundant  in  many  of  the  mines,  and  usually  valuable  for 
the  gold  and  silver  it  contains.  Beautiful  cubical  crystals  in 
the  mines  of  Gilpin  County.  Dodecahedrons  and  cubo-octa- 
hedrons in  the  Josephine  mine,  Geneva  District,  Clear  Creek 
County. 


Minerals  of  Colorado.  43 


Rhombohedral  ;  usually  in  prisms  terminating  in  a  low  pyramid  ;  cn-stals 
usually  hemihedral,  being  often  unlike  at  the  opposite  extremities,  or 
hemimorphic,  and  the  prisms  often  triangular.  Sometimes  massive  com- 
pact ;  also  columnar,  coarse  or  fine,  parallel  or  divergent.  Lustre  vitreous. 
Color  black,  brownish-black,  bluish-black,  most  common  ;  blue,  green,  red, 
and  sometimes  of  rich  shades;  rarely  white  or  colorless  ;  some  specimens 
red  internally  and  green  externally  ;  and  others  red  at  one  extremity,  and 
green,  blue,  or  black  at  the  other.  Dichroic.  Transparent  —  opaque.  Py- 
roelectric.  Brittle.  H.  7-7'b.  G.  2'94-3'3.  Comp.,  black  variety,  silica 
33,  alumina  38,  lime  1  protoxyd  of  iron  24,  soda  3,  boracic  acid  1. 

Fine  black  triangular  prisms,  with  pyramidal  terminations, 
on  Bear  Creek,  imbedded  in  white  quartz.  On  Clear  Creek, 
two  miles  below  black  Hawk,  hexagonal  prisms  in  feldspar. 
At  Guy  Hill.  Five  miles  north  of  the  Platte,  on  the  road 
from  Colorado  Springs  to  Fairplay,  fine  crystals  with  termin- 
ations. 

PETZITE.     Tell  u  ride  of  Gold  and  Silver. 

Orthorhombic.  Massive;  compact  or  fine-grained  ;  rarely  coarse-granu- 
lar. Lustre  metallic.  Color  between  steel-gray  and  iron-black,  sometimes 
with  pavonine  tarnish.  Streak  iron-black.  Brittle.  H.  2'5.  G.  8'72- 
8'83.  Comp.,  tellurium  35,  silver  47,  gold  18. 

In  Boulder  County,  associated  with  other  tellurium  ores. 


Orthorhombic;  occurs  in  short  tabular,  six-sided  prisms,  with  the  bases 
triangularly  striated  parallel  to  alternate  edges.  Cleavage  basal,  imper- 
fect. Also  massive  and  disseminated.  Lustre  metallic.  Color  iron-black; 
in  thin  crystals  cherry-red  by  transmitted  light.  Streak  iron-black.  Frac- 
ture uneven.  H.  2-3.  G.  6'214.  Analysis  of  polybasite  from  Terrible 
mine,  Georgetown,  by  Dr.  Genth  :  sulphur  16'70,  antimony  10'18,  arsenic 
0'78,  silver  02'70,  copper  9'57,  iron  0  97. 

In  small  quantity  in  many  of  the  silver  mines.  Fine  crys- 
tals in  the  Little  Emma  and  Colorado  Central  mines,  George- 
town. 

TEXRAHEDRIXE.     Gray  Copper.     Freibergite.     Fahlerz. 

Isometric;  tetrahedral;  occurs  crystallized  in  modified  tetrahedrons,  and 
also  in  compound  crystals;  also  massive;  granular,  coarse  or  fine.  Lustre 
metallic.  Color  between  light  flint-gray  and  iron-black.  Streak  generally 
same  as  the  color:  sometimes  inclining  to  brown  and  cherry-red.  Opaque; 
sometimes  subtranslucent  in  very  thin  splinters,  transmitted  color  cherry- 
red.  Fracture  subconchoidal  —  uneven.  Rather  brittle.  H.  3-4'5.  G.  4'5, 
5'11.  Comp.,  varies;  freiberyite,  the  argentiferous  variety,  sulphur  21  to  30, 
antimony  17  to  28,  copper  14  to  36,  iron  1  to  7,  zinc  1  to  6,  silver  3  to  31. 

Largely  disseminated  through  nearly  all  sulphide  silver 
ores  in  the  state.  That  from  the  mines  about  Georgetown 
carries  from  20  to  30  per  cent  of  silver,  while  that  from  con- 
tiguous districts,  3  or  4  miles  from  Georgetown,  carries  only 
i  or  2  per  cent  of  silver.  Good  crystals,  having  pavonine 
tints,  in  the  Champion  lode,  Geneva  District,  Clear  Creek 
County. 


44  Minerals  of  Colorado. 


Chalybite.  Spathic  Iron.  Carbonate  of  Iron. 
Bhombohedral  ;  occurs  in  obtuse  rhombohedrons,  whose  faces  are  often 
curved,  in  acute  rhombohedrons,  sometimes  perfect,  or  having  the  terminal 
angles  replaced,  and  in  lenticular  crystals;  also  in  botryoidal  and  globular 
forms,  subfi  brous  within,  occasionally  silky  fibrous  ;  often  cleavable  mass- 
ive, with  cleavage  planes  undulating  ;  coarse  or  fine  granular.  Lustre  vit- 
reous, more  or  less  pearly.  Color  ash-gray,  yellowish-gray,  greenish-gray, 
also  brown  and  brownish-red,  rarely  green,  and  sometimes  white.  Streak 
white.  Translucent  —  subtranslucent.  Fracture  uneven.  Brittle.  H.  3'5- 
4'5.  G.  3'7-3'6.  Comp.,  carbonic  acid  37'9,  protoxyd  of  iron  62'1. 

Of  frequent  occurrence  in  the  mines,  both  massive  and  crys- 
tallized. 

CYAXIfE. 

Triclinic;  usually  in  long-thin-bladed  crystals  aggregated  together,  or  pen- 
etrating the  gangue;  crystals  sometimes  short  and  stout.  Lateral  cleav- 
age distinct.  Sometimes  fine  fibrous.  Lustre  vitreous  —  pearly.  Color 
blue,  white,  blue  along  the  center  of  the  blades  with  white  margins;  also 
gray,  green,  black.  Streak  uncolored.  Translucent  —  transparent.  H.  5-.7 
G.  3'6-3'7.  Comp.,  silica  37,  alumina  63. 

Occurs  in  the  quartzite  of  Medicine  Bow  Peak. 

TBTRAOYMIXE.     Telluric  Bismuth. 

Hexagonal  ;  crystals  often  tabular.  Cleavage  basal,  very  perfect.  Also 
massive,  foliated  or  granular.  Lustre  metallic,  splendent.  Color  pale 
steel-gray.  Laminae  flexible.  Soils  paper.  H.  l'5-2.  G.  7'2-7'9.  Comp  , 
tellurium  48,  bismuth  52. 

At  Gold  Hill,  Boulder  County,  associated  with  other  tel- 
lurium ores. 


Phosphate  of  Yttria.  W.  E.  Hidden,  Am.Jr.Sc.,  March,IS8a. 
Tetragonal  ;  primary  form  a  rectangular  prism  with  a  square  base  ;  occurs 
in  square  octahedrons,  with  perfect  prismatic  cleavage.  Color  yellowish- 
brown,  reddish-brown,  hair-brown,  flesh-red,  grayish-white,  pale  yellow. 
Streak  pale  brown,  yellowish  or  reddish.  Opaque.  Fracture  uneven  and 
splintery.  H.  4-5.  G.  4'45-4'56.  Comp.,  phosphoric  acid  37'86,  yttria 
62-14.  " 

Small  chocolate-brown  crystals  west  of  Cheyenne  Mountain, 
El  Paso  County,  from  same  locality  as  tysonite  and  bastnasite. 

TORBERNI'TE.     Copper-Uranite. 

Tetragonal  ;  in  square  tables,  often  with  replaced  edges.  Cleavage  basal, 
highly  perfect,  micaceous.  Lustre  pearly  —  adamantine.  Color  emerald- 
and  grass-green,  and  sometimes  leek-,  apple-  and  siskin-green.  Streak 
somewhat  paler  than  the  color.  Transparent  —  subtranslucent.  Sectile. 
Laminae  brittle  and  not  flexible.  H.  2-2'5.  G.  3'4-3'6.  Comp.,  phospho- 
ric acid  15'7,  oxyd  of  uranium  62'7,  lime  6'1,  water  15'5. 

Sparingly  in  the  Peabody  lode,  Georgetown. 

BROMYRIXB.     Bromic  Silver.     Bromid  of  Silver. 

Isometric  ;  occurs  in  cubes,  octahedrons  and  cu  bo-octahedrons  ;  but  gen- 
erally in  small  concretions.  Lustre  splendent.  Color  when  pure,  bright 
yellow  to  amber  colored,  slightly  greenish  ;  often  grass-green  or  olive- 
green  externally.  Sectile.  H.  2-3.  G.  5'8-6.  Comp.,  bromine  42'6, 
silver  57*4. 
Occasionally  found  in  the  mines  at  L/eadville. 


Minerals  of  Colorado.  45 

COAL. 

The  distinguishing  characters  of  mineral  coal  are  as  follows :  Compact 
massive,  without  crystalline  structure  or  cleavage;  sometimes  breaking 
with  a  degree  of  regularity,  but  from  a  jointed  rather  than  a  cleavage 
structure.  Sometimes  laminated ;  often  faintly  and  delicately  banded,  suc- 
cessive layers  differing  slightly  in  lustre.  Lustre  dull  to  brilliant,  and 
either  earthy,  resinous  or  submetallic.  Color  black,  grayish-black,  brown- 
ish-black, and  occasionally  iridescent;  sometimes  dark  brown.  Opaque. 
Fracture  conchoidal — uneven.  Brittle;  rarely  somewhat  sectile.  Infus- 
ible to  subfusible;  but  often  becoming  a  soft,  pliant,  or  paste-like  mass 
when  heated.  On  distillation  most  kinds  afford  more  or  less  of  oily  and 
tarry  substances,  which  are  mixtures  of  hydrocarbons  and  paraffin.  Hard- 
ness" 0-5—2-5.  Gravity  1— 1'80. 

The  varieties  depend  partly  (i)  on  the  amount  of  the  vol- 
atile ingredients  afforded  on  destructive  distillation;  or  (2)  on 
the  nature  of  these  volatile  compounds,  for  ingredients  of  sim- 
ilar composition  may  differ  widely  in  volatility;  (3)  struct- 
ure, lustre,  and  other  physical  characters.  The  following 
varieties  are  found  in  Colorado: 

BR.OWIV    COAL.      Lignite. 

Sometimes  pitch-Mack,  but  often  rather  dull  and  brownish-black.  Fragile 
compared  with  anthracite.  Occasionally  somewhat  lamellar  in  structure. 

The  lignite  coal  area  of  Colorado  extends  from  St.  Vrains 
on  the  north  to  the  Raton  Mountains  on  the  south,  about  220 
miles  in  length,  and  varying  from  20  to  35  miles  in  breadth 
along  the  eastern  base  of  the  mountains.  Large  portions  of 
this  field  have  been  swept  away  by  floods  resulting  from  melt- 
ing glaciers.  The  principal  developments  of  this  vast  field 
have  been  made  in  the  vicinity  of  Boulder,  Erie,  L/oveland, 
Golden,  Colorado  Springs,  Coal  Creek,  Canon  City,  Walsen- 
burg  and  Trinidad.  Lignite  also  exists  in  North  Park  and 
at  various  points  on  the  divide  between  North  and  Middle 
Parks.  The  following  analyses  have  been  made: 

Water.  Volatile  Fixed  Ash.        Sul- 

Matter.  Carbon.  phur. 

Coal  Hill,  North  Park 18'35  32'20  41'90  6'45        1.10 

do                do         8-82  41-56  4M7  6'00        2'45 

Red  Hill,           do         15'20  3330  48'00  3'50 

do                do         10-50  37-30  50'30  1'90 

No.  1,                 do         13-20  9-30  72-00  5'50 

Erie  Mine.  Weld  County 14'80  34'50  47'30  3'40 

Marshal  Mine,  Boulder  County  .- 1200  26'00  59'20  2'80 

Murphy  Mine,  Jefferson  County 13'83  35'88  44'40  5'85 

Golden,                   do            do  " 13'43  37'15  45'57  3'85 

Franceville,  El  Paso  County.... 12'90    .     29'10  46'00  12'00 

Cutler  banks,  Uncompahgre  County  ...     7'26  43*42  41'72  7'60 

JET. 

Jet  is  a  black  variety  of  brown  coal,  compact  in  texture,  and  taking  a  good 
polish,  whence  its  use  in  jewelry. 

Occurs  in  seams,  from  one-half  to  six  inches  in  width,  in 
the  shale  about  Canon  Citv  and  Little  Fountain  Creek. 


46  Minerals  of  Colorado. 

BIXUIJ11XOIJS    COAI,. 

Bituminous  coals  have  the  common  characteristic  of  burning  in  the  fire 
with  a  yellow,  smoky  flame,  and  giving  out  on  distillation  hydrocarbon 
oils  or  tar.  They  have  usually  a  bright,  pitchy,  greasy  lustre.  The  cak- 
ing variety  becomes  pasty  or  semi-viscid  in  the  fire.  The  softening  takes 
place  at  the  temperature  of  incipient  decomposition,  and  is  attended  with 
the  escape  of  bubbles  of  gas.  On  increasing  the  heat,  the  volatile  products 
which  result  from  the  ultimate  decomposition  of  the  softened  mass  are 
driven  off,  and  a  coherent,  grayish-black,  cellular,  or  fritted  mass  (coke)  is 
left.  A  caking  coal  will  lose  its  caking  quality  if  kept  heated  for  2  or  3 
hours  at  300°C.,  and  sometimes  on  mere  exposure  for  a  time  to  the  air. 
Non-caking  coal  is  like  the  preceding  in  all  external  characters,  and  often 
in  ultimate  composition  ;  but  burning  freely  without  softening.  The  coke 
is  not  a  proper  coke,  being  in  powder,  or  of  the  form  of  the  original  coal. 

The  Trinidad  group  of  mines,  embracing  those  in  the  im- 
mediate vicinity  of  Trinidad  with  those  of  ElMoro  and  Stark- 
ville,  and  the  mines  at  Crested  Butte,  are  the  most  important 
of  this  class  in  the  State.  Durango,  Aspen  and  Rico  are 
other  localities  of  its  occurrence. 


Water.   Volatile      Fixed 
Matter.     Carbon. 
•95        29'82        56'41 

Ash. 

12-82 
4-32 
6-30 
4-47 
3-09 

...     '26        29'66        65'76 

....  3'23        40'93        49-54 

....  3'70        30'97        61'07 

,     -44        24-17        72-30 

SEMI-  BITUMINOUS. 

Col.  Coal  and  Iron  Co.,  Park  County 5'03         35'85         50'97  8'15 

Oak  Creek,  do  672        3476        5270          5'82 

Semi-bituminous  coal  is  found  principally  in  the  mountain- 
ous part  of  the  state,  The  mines  at  Como  on  the  South  Park 
railway  are  the  most  productive  of  this  class.  A  good  vein 
has  also  been  opened  up  on  Mt.  Carbon,  17  miles  north-west 
of  Gunnison  City.  The  coal  from  Walsenburg  is  by  many 
regarded  as  belonging  to  this  class. 


Color  jet-black  ;  vandyke-brown  when  powdered.  Has  the  appearance  of 
bituminous  coal.  Does  not  slack  or  break  to  pieces.  In  composition 
much  like  albertite  and  torbanite.  G.  1'323.  Analysis  by  E.  J.  Mallett: 

Water  6'02 

Volatile  matter 39'95 

Fixed  carbon  and  ash 54'03— lOO'OO 

The  locality  of  this  new  coal  species  is  Middle  Park.  It  is 
a  caking  bituminous  coal  but  yields  an  imperfect  coke.  In 
comparison  with  English  cannel  coal  it  gives  thirty  per  cent 
more  gas  of  a  high  illuminating  power.  It  is  named  after 
Mr.  W.  N.  Byers. 

NATIVE    COKE. 

More  compact  than  artificial  coke,  and  sometimes  affording  considerable 
bitumen. 

The  origin  of  native  coke  is  attributed  to  the  action  of  a 


Minerals  of  Colorado.  4j 

trap  eruption  on  bituminous  coal.  It  has  been  found  near 
Crested  Butte  where  a  dike  of  lava  has  intruded  the  coal 
strata.  It  has  also  been  found  at  Trinidad. 

ANTHRACITE;. 

Lustre  bright,  often  submetallic,  iron-black,  and  frequently  iridescent. 
Fracture  conchoidal.  Volatile  matter  afttr  drying  3  to  6  per  cent.  Burns 
with  a  feeble  flame  of  a  pale  color.  H.  2-2'5. 

Anthracite  coal  appears  to  be  confined  mainly  to  the  coal 
basins  in  the  Elk  Mountains,  and  extends  over  a  large  scope 
of  country.  These  mountains  are  composed  of  lofty  peaks  of 
eruptive  rock,  and  are  separated  from  the  plains  by  three  par- 
allel ranges,  the  Colorado  or  Front  Range,  the  Park  Range 
and  the  Saguache  Range,  separated  from  one  another  by 
trough-like  valleys  and  parks.  The  coal  fields  are  in  the 
same  geological  horizon  as  that  of  the  plains,  and  the  coal 
is  much  the  same,  metamorphosed  or  changed  by  heat  into 
anthracite,  and  on  the  outer  edges  of  the  basins  graduates 
into  lignite.  On  Anthracite  Mesa,  near  Crested  Butte,  the 
veins  are  from  two  to  ten  feet  thick.  Analyses  show 

Water.   Volatile    Fixed  Ash. 

Matter.  Carbon. 

Crested  Butte,  Gunnison  County  .......................  T20        5'16        90*24  3'40 

Anthracite  Creek,             do           .......................  2'00         2'50         9190  3'60 

Anthracite  Mesa,             do          .......................          5'17               90'85  4'18 

Rock  Creek,                      do           .......................           7'40               88'90  3'68 

SEMI-ANTHRACITE. 

W.  &  D.  Trust  Co.,  Crested  Butte  .....................  4'00       14'00        74'00        8'00 

Uncompahgre  Canon  .....................................  1/86       10'70        77'32       1012 

PETRO1LBUM.     Naptha.     Mineral  Oil.     Kerosene. 

A  fluid  bitumen  of  dark  color,  which  oozes  from  certain  rocks  and  becomes 
solid  on  exposure,  forming  asphaltum.  Com.,  carbon  82'2,  hydrogen  14'8. 

Oozes  from  sandstone  near  Morrison.  Six  oil  wells  are  in 
operation  in  the  neighborhood  of  Canon  City  and  Florence,  in 
Fremont  county.  The  Oil  Creek  well,  which  was  sunk  in 
1862,  turned  out  about  3,000  gallons  of  oil. 

ASPHAI/TUM.     Bitumen.     Mineral  Pitch. 

Amorphous.  Lustre  like  that  of  black  pitch.  Color  brownish-black  and 
black.  Odor  bituminous.  Melts  ordinarily  at  90°  to  100°  C.,  and  burns 
with  a  bright  flame.  Soluble  mostly  or  wholly  in  oil  of  turpentine,  and 
partly  or  wholly  in  ether;  commonly  partly  in  alcohol.  The  more  solid 
kinds  gradate  into  the  pittasphalts  or  mineral  tar,  and  through  these  is  a 
gradation  to  petroleum.  Comp.,  carbon  75'0,  hydrogen  9'5,  oxygen  15'5. 

Fluid  bitumen  oozes  from  sandstone  near  Morrison  and 
forms  an  earthy  asphaltum.  In  the  White  River  region  and 
near  Canon  Cit. 


RKSIN. 

•  Mineral  resin  occurs  Jin  the  coal  in  scales,  and  small  masses 
have  been  found  in  the  soil  on  the  Table  Mountains,  but  the 


48  Minerals  of  Colorado. 

species  have  not  been  determined.  Prof.  Wm.  P.  Headden 
mentions  the  occurrence  of  a  substance  in  coal  from  the 
Mitchell  mine,  Brie,  which  he  believes  to  be  napthaline.  It 
occurs  in  microscopic,  tabular  crystals,  which  are  thin,  color- 
less and  transparent. 

TURGIXB. 

Compact  fibrous  and  divergent,  to  massive;  often  botryoidal  and  stalactitic 
like  limonite.  Also  earthy,  as  red  ochre.  Lustre  submetallic  and  some- 
what satin-like  in  the  direction  of  the  fibrous  structure;  also  dull  earthy. 
Color  reddish-black,  to  dark  red  ;  bright-red  when  earthy  ;  botryoidal  sur- 
face often  lustrous,  like  much  limonite.  Opaque.  H"  5-6.  G.  S'56-3'74. 
Comp.,  Sesquioxyd  of  iron  94*7.  water  5'3. 

Occurs  in  small  botryoidal  masses,  of  reddish-black  color, 
and  highly  polished  surfaces,  at  Florissant,  associated  with 
gothite,  amazonstone,  smoky  quartz,  etc. 


Iron-Alumina  Garnet.  Precious  or  Oriental  Garnet. 
Isometric;  occurs  in  dodecahedrons  and  trapezohedrons,  both  forms  some- 
times variously  modified  ;  rarely  in  octahedrons.  Cleavage  parallel  to 
the  faces  of  the  dodecahedron.  Also  found  massive.  Color  fine  deep-red 
and  transparent,  and  then  ealled  precious  garnet;  also  brownish-red,  and 
translucent  or  subtranslucent.  Streak  white.  Lustre  vitreous  —  resinous. 
Fracture  subconchoidal,  uneven.  H.  6'5-7"5.  G.  4'13.  Comp.,  silica  36'1, 
alumina  20*6,  protoxyd  of  iron  43  '3. 

L/arge  and  perfect  dodecahedrons,  some  of  them  measuring 
six  inches  in  diameter,  occur  in  chlorite  near  Salida,  Chaffee 
County.  Several  thousand  specimens  have  been  taken  out 
of  a  single  "pocket."  They  are  usually  coated  with  chlorite, 
and  the  surfaces  of  the  garnets  are  decomposed,  the  decempo- 
sition  product  forming  aphrosiderite.  The  color  of  the  garnet 
is  brownish-red.  Analysis  by  S.  L.  Penfield  and  F.  L/.  Sperry 
gave  the  following: 

Silica  ......................................  37-61 

Alumina  .................................  2270 

Protoxyd  of  Iron  ......................  33'83 

Protoxyd  of  Manganese  ..............     1*12 

Magnesia  .................................     3'61 

Lime  ......................................     1'44 


100-31 

Beautiful  dark  red  garnets,  which  can  probably  be  classed 
as  precious  garnets,  are  abundant  in  the  placers  at  Fairplay 
and  Breckenridge.  The  are  usually  quite  small  and  of  no 
value  as  gems. 

APHROSIDBRITE. 

A  soft  ferruginous  chlorite,  of  a  dark  olive-green  color,  scaly  massive  in 
structure ;  the  scales  minute,  transparent,  and  hexagonal. 

Occurs  as  an  alteration  product  on  the  garnets  found  at  Sa- 
lida, forming  a  coating-  of  light  green  color.  Analysis  by 
Penfield  and  Sperry  gave: 


Minerals  of  Colorado.  49 

Silica  ......................................  28-20 

Alumina  .................................  22'31 

Protoxydof  Iron  .......................  19'11 

Protoxyd  of  Manganese  ..............  17*68 

Lime  .....................................  '48 

Soda  ......................................  72 

Potassa  ...............  ..  ...................  1'03 

Water  ....................................  10'90 

FAYAI^IXB.     Iron  Chrysolite.     Anhydrous  Silicate  of  Iron. 

Massive,  crystalline.  Cleavage  in  two  directions  at  right  angles  to  one 
another.  Lustre  metalloid,  somewhat  resinous  in  the  fracture.  Color 
black  ;  sometimes  iridescent.  Opaque.  Fracture  imperfectly  conchoidal. 
Attractable  by  the  magnet.  H.  6'5.  G.  4-414.  Com  p.,  silica  29'5,  pro- 
toxyd  of  iron  70'5. 

Occurs  in  quite  large  masses  in  Cheyenne  Canon,  El  Paso 
County. 

FIRROWTK. 

Monoclinic  ;  crystals  commonly  long  and  slender.  Cleavage  brilliant  and 
perfect.  Also  occurs  fibrous  or  columnar  massive,  sometimes  radiating. 
Lustre  vitreous,  subadamantine.  Color  hair-brown,  grayish-brown,  gray- 
ish-white, grayish-green,  pale  olive-green.  Streak  uncolored.  H.  6-7. 
G.  3-2.  Comp.,  silica  36'8,  alumina  63'2. 

Occurs  in  small  fibrous  masses,  of  grayish-green  color,  on 
Sherman  Mountain,  near  Georgetown. 

SAXIDIK.     Glassy  Feldspar.     Whitman  Cross,  Am.  Jr.  Sc.,  Feb.,  1884. 

A  variety  of  orthoclase  (p.12)  occurring  in  transparent  glassy  crystals, 
mostly  tabulur,  in  eruptive  rock. 

Mr.  Cross  describes  the  occurrence  of  sanidin  in  the  nevad- 
ite  of  Chalk  Mountain,  and  rhyolite  of  Ragged  Mountain, 
which  possesses  a  satin  lustre.  Smoky  quartz  and  topaz  are 
associates  of  the  sanidin  in  the  nevadite.  Also  occurs  in  rhy- 
olite at  Nathrop,  with  the  same  associate  minerals. 


Pearl  Spar.  Brown  Spar.  Magnesian  Limestone. 
Rhombohedral  ;  crystals  often  having  curved  faces.  Cleavage  perfect 
parallel  to  the  primary  faces.  Often  granular  and  massive,  constituting 
extensive  beds.  Color  white  or  tinged  with  yellow,  red,  green,  brown  and 
sometimes  black.  Lustre  vitreous  or  a  little  pearly.  Nearly  transparent 
to  translucent.  Brittle.  H.  3'5-4.  G.  2'8-2'9.  Comp.,  carbonate  of  lime 
54'35,  carbonate  of  magnesia  45'65. 

Occurs  in  extensive  beds  in  various  portions  of  the  State, 
and  in  small  quantities  in  the  mines,  frequently  crystallized. 


Acanthite,  13 

Bismuthinite,  9 

Chrysolite,  37 

Actinolite,  30 

Bismutite,  35 

Citrine,  24 

Agate,  18 

Bitumen,  47 

Cobalt,  Arsenate,  30 

Agatized  Wood,  18 

Bituminous  Coal,  46 

Arsenide,  8 

Alabaster,  26 

.B/ac&  Tellurium,  38 

Iftoom,  30 

Alabandite,  35 

Black  Lead,  27 

Columbite,  19 

Alaskaite,  8. 

Blende,  25 

Coloradoite,  31 

Allanite,  21 

Bloodstone,  17 

Common  Mica,  35 

Alamandite,  48 

.B/we  Carbonate  Copper,  40 

Common  Salt.  25 

yl/oite,  12 

£ke  yftno/,  31 

Copper,  Carbonate,  36,  40 

Allophane,  21 

tfo/e,  17 

O/ance,  37 

^4/toite,  21 

Bornite,  14 

Native,  6 

vlfotra,  Native,  23 

Bromyrite,  44 

Oxide,  40 

Amazonstone,  12 

Brochantite,  10 

Pyrites,  9 

Amethyst,  23 

Bromid  of  Silver,  44 

SiJieate,  29 

Amphibole,  30 

Bromic  Silver,  44 

Sulphate,  10,  31 

Analcite,  15 

Brown  Coal,  45 

Sulphide,  37 

Anglesite,  7 

Brown  Iron  Ore,  41 

Uranite,  44 

Annabergite,  37 

Brown  Ochre,  33 

CosaMe,  13 

Anthracite,  47 

Brown  Spar,  49 

Covellite,  19 

Antimony  Glance,  23 

Byerite,  46 

Cryolite,  11 

Aphrosiderite,  48 

Cuprite,  40 

Apophyllite,  15 
Aquamarine,  41 

Cairngorm,  24 

Cyanite,  44 

Aragonite,  42 
Arfvedsonite,  22 
Argentite,  13 
Argentine,  39 
Arsenide  of  Cobalt,  8 

Calaverite,  29 
Ca/ctte,  39 
Calcareous  Spar,  39 
Carnelian,  17 
Carbonate  Bismuth,  35 

7)ar^  fled  StVwer  Ore,  19 
Dechenite,  38 
Desdoizite,  39 
Dolomite,  49 

J.T01l>)   u 

Arsenopyrite,  40 
Arsenical  Pyrites,  40 
Ar  senate  of  Nickel,  37 
Arsenical  Nickel,  7 
Asbestus,  30 
Asphaltum,  47 
Astrophyllite,  32 
Autunite,  13 

Soda,  34 
7ron,  44 
Baryta,  38 
Copper,  40 
Lead,  36 

Manganese,  10 
Gassiterite,  21 
G&sfo'te,  25 

Egyptian  Jasper,  24 
Elpasolite,  20 
Embolite,  42 
Enargite,  13 
Epid'ote,  36 
Erythrite,  30 
Erubescite,  14 
J5<ye  ,4  pate,  18 

^iiZttTitC)  40 

Cerargyrite,  24 

FaMerz,  43 

Cerussite,  36 

Fa/se  Topaz,  24 

Banded  Agate,  IS 

Chabazite,  14 

Fayalite,  49 

Barite,  38 

Chalcanthite,  31 

Feldspar,  12 

Bastnasite,  41 

Chalcedony,  14 

FtrroteUurite,  29 

Beegerite,  8 

Chalcocite,  37 

Fibrolite,  49 

Beryl,  41 

Chalcopyrite,  9 

Fibrous  Gypsum.,  26 

Biotite,  35 
Bismuth,  Carbonate,  35 
Glance,  9 

Chalybite,  44 
CAes.st/  Copper,  40 
CMort'd  o/  /Si/twr,  24 

Fibrous  Heavy  Spar,  25 
I'  ire  OpaZ,  41 
Fluorite,  Fluor  Spar,  10 

Native,  6 

Sodium,  25 

Foliated  Tellurium,  38 

S/foer,  32 

Chrysocolla,  29 

Fortification  Agate,  18 

Sulphide,  9 

Vhn/soprase  18 

Freibergite,  43 

INDEX. 

Gadolinite,  26 

Levynite,  16 

Nickel  Green,  37 

Gahnite,  22 

Lt<7/&<  JFfat&y  Silver  Ore,  1  9 

OcAre,  37 

Galenite,  Galena,  38 

Lignite,  45 

Telluride,  7 

Garnet,  33 

Lime  Uranite,  13 

Niccolite,  7 

Gearksutite,  11 

Limonite,  33 

Glassy  Feldspar,  49 
GWd,  5 

Lionite,  29 
Lollingite,  9 

Oblique  Mica,  35 
Octahedral  Iron  Ore,  34 

Gothite,  41 

Oiivene,  37 

Graphite,  27 
Graphic  Tellurium,  32 
Crrai/  Copper,  43 
Green  Carbonate  Copper,  36 
#reen  Lead  Ore,  37 

Magnetite,  34 
Malachite,  36 
Manganese,  Carbonate,  10 
6?ame«,  36 
Sulphate,  31 

Ora/z,  18 
OpaZ,  40 
Oriental  Garnet,  48 
Orthodase,  12 

Guitermanite,  9 
Gypsum,  26 

ITaftte,  25 

Heavy  Spar,  38 
Heliotrope,  17 
Hematite,  34 
Hessite,  28 

Sulphide,  35 
Magnesian  Limestone,  49 
Magnetic  Iron  Ore,  34 
Magnesia  Mica,  35 
Magnesia  Alum,  23 
Magnolite,  29 
JfairWe,  39 
Melonite,  7 

Pachnolite,  11 
Pear/  Spar,  49 
Peridot,  37 
Petroleum.  47 
Peteite,  43 
Phenacite,  7 
Phosphate  of  Lead,  37 

TT-,  ,      •            ,«   * 

Hexagonal  Mica,  35 
Hornblende,  30 
LTorn  Silver,  24 
Hubnerite,  17 
Hyalite,  41 

Mendozite,  31 
Mesolite,  16 
Mercury,  Native,  5 
Telluric,  44 
Telluride,  29,  31 
Micaceous  Iron  34 

Yttna,  44 
Pickeringite,  20 
Pitchblende,  28 
Pitchstone,  12 
Plumbago,  27 
Polybasite,  43 

Iceland  Spar,  39 
Idocrase,  40 
Ilesite  31 

Microclin,  12 
Mineral  Coal,  45 
Oi/.  47 

Porcelain  Clay,  39 
PofasA  ,4/?/m,'28 
Potas/t  Feldspar,  12 

/ran,  Arsenide,  9 
Arsenical,  40 
Carbonate,  44 
Chrosolite,  49 
Columbate,  19 
<?ame«,  48 
Oxide,  33,  34,  41,  48 
Pyrites,  42 
Silicate,  49 
Sulphate,  7 
Sulphide,  42 

PiteA,  47 
Resin.  47 
Mispickel,  40 
J/ocAa  Stone,  18 
Molybdenite,  25 
.Moss  ^4<7a<e,  18 
Morion,  24 
Mutter's  Glass,  41 
Muriate  of  Soda,  25 
Muscovite,  35 

Potash  Mica,  35 
Prase,  18 
Precious  Garnet,  48 
Prosopite,  11 
Proustite,  19 
Protoxyd  of  Uranium,  28 
Ptilolite,  42 
Purple  Copper  Ore,  14 
Pyrargyrite,  19 
Pyromorphite,  37 
Pyrite,  42 

Nagyagite,  38 

Jarosite,  7 

Naptha,  47 

Qwarte,  23 

Jasper,  24 

Natrolitc.  16 

Quicksilver,  5 

Jet,  45 

Natron,  34 

Native  Alum,  23 

Radiated  Zeolite,  14 

Kalinite,  23 

Bismuth,  6 

Rcdstonite,  19 

Kaolinite,  39 

(Me,  46 

.Red  Oo6a/«  Ore,  30 

Kerosene,  47 

Copper,  6 

^ed  OcAre,  34 

Kobellite,  27 

6rO/d,    5 

.Red  Oxide  o/  Copper,  40 

Mercury,  5 

^ed  ASi/uer  Ore,  19 

Laumonite,  15 

Silver,  5 

Rhodochrosite,  10 

Lead,  Carbonate,  36 

Sulphur,  6 

Ribbon  Jasper,  24 

Phosphate,  36 

Tellurium,  <> 

JRoefc  Crystal,  23 

Sulphate,  7 

iVeed/e  Zeofo'fe,  16 

Rock  Salt,  25 

Sulphide,  38 
Telluride,  21,  38 

Nephelite,  37 
Nickel,  Arsenate,  37 

Roscoelite,  27 
•  ^ose  Quartz,  24 

Vanad,ate,  38,  39 

Arsenical,  7 

Kw6t/  Sifoer  Ore,  19 

INDEX. 


Sanidin,  49 

Sulphate  of  Lime,  26 

Tourmaline,  43 

Salt,  25 

Manganese,  31 

Tremolite.  30 

Sardonyx,  18 

Strontia,  25 

Tysonite,  42 

Satin  Spar,  26 

Sulphide  of  Antimony,  23 

Tungstate  of  Lime,  27 

Schedite,  27 

Bismuth,  7 

Magnesia,  17 

Schirmerite,  32 

Copper,  19 

Manganese,  28 

Scolecite,  16 

/row,  42 

Z\*r$r;te,  48 

£e/enite,  26 

£ead,  38 

Siderite,  44 
Siftcafe  o/  Iron,  49 

Manganese,  35 
Molybdena,  25 

Uraninite,  28 

Silver,  Chloride,  24 
Chloro-  Bromide,  42 

tfiteer,  13, 
Zirac,  25 

Vesuvianite,  40 

Bismuth,  32 

Sulphur,  Native,  6 

FV^-eows  Copper  Ore,  37 

£M?,  14 

Sylvanite,  32 

Volcanic,  Glass,  12 

Bromic,  44 

frlnnrc    1  '•? 

\jriUjliLti,   -LO 

Native,  5 

Telluric  Bismuth,  44 

tfito'te  iea^  Ore,  36 

Sulphide,  13 
Telluride,  29,  32 
Smaltite,  8 
Smoky  Quartz,  24 

Teilurious  Acid,  29 
Telluride  of  Gold,  29 
.  £ead,21 
Mercury,  29,31 

Willemite,  31 
Witherite,  38 
Wolframite,  28 
Food  OpaJ  41 

/Soda  J.^m,  31 

Mdfce/,  7 

Specular  Iron,  34 

Tellurite.  29 

Xenotime,  44 

Spessartite,  36 

Tellurium,  Native,  6,  29 

Spathic  Iron,  44 
Sphalerite,  25 
Sphene,  37 
Stibnile,  23 
,»ite,  14 

Tennantite,  8 
Tetradymite,  44 
Tetrahedrite  43 
Thomsenolite,  1  1 
Thomsonite,  15 

Zinc  Blende,  25 
Silicate,  27,  31 
Spme/,  22 
Sulphide,  25 

Sulphate  of  Baryta,  38 
Copper,  31 
/row,  7 

Tm  ^tone,  21 
Titanite,  37 
Topaz,  22 

Zinkenite,  8 
Zircon,  2C 
Zunyite,  12  ' 

Lmd,  7 

Torbernite,  44 

E3VSTATITE.     Bronzite.     Protobastite.     W.  Cross,  Bulletin  No.  1,  U.  S. 

Geological  Survey. 

Orthorhombic;  primary  form  an  oblique  four-sided  prism  with  a  very  dis- 
tinct cleavage  parallel  to  the  lateral  planes;   sometimes  a  fibrous  appear- 
ance on  the  cleavage  surface;  also  occurs  massive  and  lamellar.     Lustre  a 
little  pearly  on  the  cleavage-surfaces  to  vitreous;    often  metalloidal  in  the 
"bronzite  variety.     Color  grayish-white,  yellowish-white,  greenish-whits,  to 
olive-green   and    brown.     Streak    uncolored,   grayish.     Double  refraction 
positive.     H.  5'5.     G.  31  —  3'3.     Composition  : 

Silica  ....................................   60 

Magnesia  ..............................  40 

Sometimes  iron,  alumina,  etc.  - 

100 

Whitman  Cross  gives  the  occurrence  of  an  enstatite-bearing 
diabase  in  a  narrow  dike  of  dark  rock  at  Morrison. 


Iron  Potash  Mica. 
Hexagonal  ;  occurs  in  small  six-sided  tables,  or  an  aggregation  of  minute 
opaque  scales,  with  perfect  basal  cleavage.  Lustre  adamantine,  inclining 
to  vitreous,  pearly.  Color  black  with  occasionally  a  leek-green  reflection. 
Streak  grayish-green.  Opaque  or  translucent  in  very  thin  laminae.  Some- 
what brittle,  or  but  little  elastic.  H.  3.  G.  3.  Composition  : 

Silica  ................................  37-40 

Alumina  ...........................  1T60 

Peroxide  of  Iron  .................  27'66 

Protoxide  of  Iron  .................   12'43 

Magnesia    ..........................     0'26 

Potash  .............................     9-20 

Water  ................................     0'60 


99-69 

According  to  Hague,  some  of  the  mica  in  the  granite  of  the 
eastern  Colorado  range  is  lepidomelane. 


Manganese  Spar,  Bisilicate  of  Manganese. 
Triclinic,  and  like  pyroxene,  with  a  cleavage  in  three  directions,  two  of 
which  are  perpendicular  to  each  other.  Usually  massive.  Lustre  vitre- 
ous. Color  light  brownish-red,  flesh-red,  sometimes  greenish  or  yellowish, 
when  impure  ;  often  black  outside  from  exposure.  Streak  white.  Trans- 
parent —  opaque.  Fracture  conchoidal  —  uneven.  ^Very  tough  when  mas- 
sive. H.  5-5—  6-5.  G.3'4—  3-ti8  Composition: 

Silica  .  ................................  45-9 

Protoxide  of  Manganese  .........  51*4 


lOO'O 

Occurs  as  a  gangue  of  light  rose  color  in  the  San  Juan  mines. 


56  APPENDIX. 

ALAMANDITE  (p.  48).  —  New  localities  in  Chaffee  County 
mentioned  by  W.  B.  Smith.  Dodecahedral  crystals  in  chlo- 
ritic  schist  from  Longfellow  gulch.  Crystals  in  limestone, 
having  the  dodecahedron  and  trapezohedron  about  equally 
developed,  from  Calumet. 

CINNABAR  is  said  to  be  found  near  Durango,  but  needs 
verification. 

BNARGITE  (p.  13).  —  Occurs  massive  and  in  slender  crystals 
in  the  Missouri  mine,  Hall  Valley,  Park  County.  Small 
masses  in  the  Centennial  mine,  Georgetown.  In  considerable 
quantity  in  the  Forest  Queen  mine,  Gunnison  County,  and  in 
the  mines  of  Red  Mountain  district,  San  Juan. 

GRAPHITE  (p.  27).  —  A  large  deposit  a  few  miles  south  of 
the  El  Moro  coal  banks,  Las  An  i  mas  County. 

NATIVE  SULPHUR  (p.  6).  —  Abundant  in  the  Spirit  mine  at 
Red  Cliff. 

PETROLEUM  (p.  47).  —  Has  been  found  on  Green  River. 

TENNANTITE  (p.  8).  —  In  large  quantities  in  the  Red  Moun- 
tain mines,  San  Juan. 

TORBERNITE  (p.  44).—  Occurs  on  Lyden  Creek  (Berthoud), 


Oxide  of  Lead. 

Occurs  pulverulent,  occasionally  exhibiting,  under  the  microscope,  cryw- 
talline  scales.  Lustre  faint  greasy,  or  dull.  Color  vivid  red,  mixed  with 
yellow.  Streak  orange-yellow.  Opaque.  H.  2  —  3.  G  4'6.  Composition; 

Oxygen  ..............................     9'34 

Lead  .............................  .....  90'66 


100-00 

Prof.  Emmons  mentions  its  occurrence  in  some  of  the  mines 
at  Leadville. 


Monoclinic  ;  primary  form  a  right  rhombic  prism.  Occurs  in  attached 
crystals  and  in  layers  and  granular  masses,  frequently  in  a  globular  form. 
Lustre  vitreous;  pearly  on  planes  of  cleavage.  Color  various  shades  of 
white,  passing  into  red,  gray  and  brown.  Streak  white.  Transparent  — 
subtranslucent.  Fracture  subconchoidal,  uneven.  Brittle.  H.  3'5  —  4, 
G.  2'2.  Composition: 

Silica  .................................  59-1 

Alumina  .............................  16'9 

Lime  .................................     9'2 

Water  .................................  14'8 

Occurs  in  small  white  glassy  crystals  in  the  augite-andesite 
on  Green  Mountain,  Jefferson  County. 


APPENDIX.  57 


Monoclinic;  priuuiry  form  a  right  rhombic  prism.  Occurs  in  attached 
crystals  and  in  layers  and  granular  masses,  frequently  in  a  globular  form. 
Lustre  vitreous  ;  pearly  on  planes  of  cleavage.  Color  various  shades  of 
white,  passing  into  red,  gray  and  brown.  Streak  white.  Transparent  — 
subtranslucent.  Fracture  subconchoidal,  uneven.  Brittle.  H.  3'5  —  4. 
G.  2'2.  Composition: 

Silica  .................................  59-1 

Alumina  .............................  16'9 

Lime  .................................     9'2 

Water  .................................  14'8 


100-0 

Occurs  in  small  white  glassy  crystals  in  the  augite-andesite 
on  Green  Mountain,  Jefferson  County. 


Carbonate  of  Strontian. 
Orthorhombic;  primary  form  a  right  rhombic  prism  ;  occurs  crystallized 
in  hexahedral  prisms,  which  are  modified  on  the  edges,  or  terminated  by 
pyramids;  often  acicular  and  in  divergent  groups;  also  occurs  in  column- 
ar-globular forms,  fibrous  and  granular.  Lustre  vitreous,  inclining  to  res- 
inons  on  uneven  faces  of  fracture.  Color  pale  asparagus-green,  apple- 
green,  also  white,  gray,  yeilow,  and  yellowish-brown.  Streak  white. 
Transparent  —  translucent.  Fracture  uneven.  Brittle.  H.  8'5  —  4.  G. 
3'605  —  3'713.  Composition: 

Carbonic  Acid  ....................  29'8 

Strontia  ..............................  70'2 


100-0 

Occurs  in  the  shape  of  small  balls  on  celestite  from  the 
the  Garden  of  the  Gods. 

SXROMEYERITE.     Sulphuret  of  Silver  and  Copper. 

Orthorhombic  ;  isornorphous  with  copper  glance.  Usually  massive.  Lus- 
tre metallic.  Color  dark  steel-gray.  Streak  shining.  Brittle.  Fracture 
subconchoidal.  H.  2'5— 3.  G.  6'2 — 6.3.  Composition,  silver,  sulphur  and 
copper  in  variable  proportions.  Partial  analyses  of  strorneyerite  from  Col- 
orado mines  returned  the  following  : 

Ag.       Cu.         S.       Fe. 

Little  Giant  mine,  Clear  Creek  Co 50'00     21'00     16'60    3'40— W.C.  Minger. 

"       "  48-00    35-00     16-00      — K.  Neuman. 

Grant  mine,  Boulder  County 38'00     29'00      •     — F.  Graham. 

Winning  Card  mine,  Summit  Co.. 49*00     36'00     IG'OO      — R.  Neuman. 

Occurs  in  small  masses  and  needle  crystals  coated  with 
chalcopyrite  in  the  Little  Giant  mine,  Clear  Creek  County. 
In  considerable  quanty  in  the  Grant  mine,  Boulder  County, 
and  in  the  Winning  Card  and  Black  Prince  mines,  Summit 
County.  A  variety  carrying  i  y2  p.  c.  silver  "is  found  in  small 
quantities  in  a  lode  on  Saxon  Mountain,  Georgetown. 

RHODOCHROSITE  (p.  10.) — Crystallized  and  fibrous  in  the 
Queen  of  the  West  mine,  near  Gray's  Peak,  associated  with 
alabandite. 


58  APPENDIX. 


Oxide  of  Titanium. 
Tetragonal  ;  occurs  in  four  or  eight-sided  prisms,  terminated  by  pyramids, 
either  single  or  geniculated,  and  often  striated  longitudinally  ;  also  in 
reticulated  masses  formed  by  acicular  and  capillary  rnacled  crystals;  also 
massive  and  imbedded.  Sttncture  lamalJar.  Color  reddish-brown,  pass- 
ing into  red,  sometimes  yellowish,  bluish,  violet,  black,  rarely  grass-green. 
Streak  pale  brown.  Lustre  metallic  adamantine.  Fracture  subconchoidal, 
uneven.  Subtransparent  —  opaque.  Brittle.  H.  6  —  6'5.  G.  4*18  —  4*25. 
Composition  :  Titanic  Acid  : 

Oxygen  .................................  39 

Titanium  ..............................  61 

100 

A  small  quartz  pebble  containing  red  rutile  was  found  in 
the  Platte  River  at  the  foot  of  the  mountains.  It  is  in  the 
collection  of  Whitman  Cross. 

COSALITE  (p.  13).  —  Analyses:  I  from  the  Alaska  mine,  Ou- 
ray  County,  by  Genth.  II  from  Ouray  County,  by  Konig: 

i.  n. 

Bismuth  ...........................  44'95  43'54 

Lead  ...............................    28'10  26'77 

Silver  ..............................     1'44  T35 

Copper  ....................  .  ........     8-00  8'22 

Zinc  ......  ...........................     0'24  ...... 

Antimony  ..........................     0'51  ...... 

Arsenic  .............................     0'04  ...... 

Selenium  ..........................   trace  ...... 

Sulphur  .............................  16-80  16-54 

100-08        96-42 

BEEGERITE  (p.  8).  —  Analyses:  I  from  Ouray  county,  by 
Konig.  II  from  the  Treasure  Vault  mine,  Geneva  District, 
Clear  Creek  County,  by  Genth. 

i.  n. 

Bismuth  ...........................  19'35  19'81 

Lead  ................................  45'87  50'16 

Silver  ..............................     9'98  15'40 

Sulphur  ...........................   13-37  14'59 

88-57        99-96 

ANNABERGITE  (p.  37).  —  Analysis  of  annabergite  from  the 
Gem  mine,  Silver  Cliff,  by  Genth: 

Arsenic   Acid  .....................  36"64 

Oxide  of  Nickel  ..................  32'64 

Oxide  of  Cobalt  ..................  O'fO 

Lime  ..................  ...............  3'51 

Magnesia  ........  .........  .....  .....  374 

Water  ..............................  23'94 


100-97 


CUPRITE  (p.  40). — Very  pure  in  veins   near   Pine   Grove, 
Platte  Canon,  associated  with  chrysocolla. 


APPENDIX.  59 

WITXICHENITE.     Cupreous  Sulphuret  of  Bismuth. 

Orthorhombic ;  occurs  massive  and  disseminated  ;  also  coarse  columnar;  or 
an  aggregate  of  imperfect  prisms.  Cleavage  in  one  vertical  direction. 
Color  steel-gray,  tin-white,  tarnishing  pale  lead-gray.  Streak  black.  H. 
3'5.  G.  5.  Composition : 

Sulphur 19-44 

Bismuth 42'11 

Copper 38-45 

100-00 

According  to  T.  B.  Comstock  wittichenite  is  of  common 
occurrence  in  the  mines  of  San  Juan  county,  and  is  rich  in 
silver. 

AIKIIVIXE.     Acicular  Bismuth.     Needle  Ore. 

Orthorhombic  ;  occurs  in  imbedded  acicular  four  or  six-sided  prisms,  in- 
distinctly terminated,  and  striated  longitudinally.  Also  massive.  Lustre 
metallic.  Color  blackish  lead  gray,  with  a  pale  copper-red  tarnish.  Frac- 
ture uneven.  H.  2 — 2'5.  G.  6'1 — 6'8.  Composition  : 

Sulphur 16-7 

Bismuth 36'2 

*  Lead 36'1 

Copper 11-0 


100-0 

Occurs  in  the  mines  of  San  Juan  County  in  beautiful  crys- 
tals, and  also  in  the  Gladiator  mine,  Hinsdale  county,  carry- 
ing about  5  per  cent  of  silver  (T.  B.  Comstock). 


Orthorhombic;  crystals  often  tabular;  also  massive  and  amorphous.  Lus- 
tre submetallic  to  vitreous  and  greasy.  Color  black,  brown,  brownish-yel- 
low, straw-yellow.  Streak  gray  to  colorless.  Opaque  to  subtranslucent. 
Fracture  small  conchoidal  to  granular.  H.  5  —  5'5.  G.  5*4  —  5*9.  Compo- 
sition : 

Tantalic  Acid  .......................  62'5 

Yttria  .................................  22'6 

Lime  ...................................     5'2 

Protoxide  of  Iron  ..................     3'4 

Protoxide  of  Uranium  ...........     6'3 


100-0 

W.  B.  Smith  mentions  the  occurrence  of  a  black  variety, 
in  small  masses,  at  Devil's  Head  Mountain,  Douglas  County. 

WAD.     Bog  Manganese. 

Occurs  in  amorphous  and  reniform  masses,  either  earthy  or  compact,  and 
sometimes  incrusting  or  as  stains.  Often  loosely  aggregated,  and  feeling 
very  light  to  the  hands.  Color  dull  black,  bluish  or  brownish-black.  H. 
0'5.  G.  3 — 4'26.  Composition,  oxide  of  manganese,  but  mixed  with 
other  ingredients. 

Occurs  in  small  quantities  in  many  localities  throughout 
the  state,  frequently  staining  the  rocks  black  at  the  surface  of 
veins,  and  sometimes  forming  beautiful  dendritic  specimens, 
called  '  'forest  rock. ' '  Quite  a  large  deposit  near  the  springs 
on  Snake  River,  Summit  County. 


60  APPENDIX. 

MYPERSXMEXE.     Metalloidal  Diallage.     Labrador  Hornblende. 

Orthorhombic;  occurs  in  foliated  masses  or  imbedded  in  rocks.  Lustre 
somewhat  pearly  on  a  cleavage  face,  sometimes  metalloidal.  Color  dark 
brownish-green,  grayish-black,  pinchbeck-brown.  Streak  grayish,  brown- 
ish-gray. Translucent  to  nearly  opaque.  Brittle.  H.  5 — 6.  G.  3'392. 
Analyses  of  hypersthene  from  Buffalo  Peaks,  Mosquito  Range,  by  Hille- 
brand : 

Silica 51703        5M57        50'043 

Alumina  1'720          2'154          2'906 

Sesquioxide  of  Iron 0'304          

Protoxide  of  Iron 17'995        18'360        J.7'812 

Protoxide  of  Manganese..     0'363          0'363          0'120 

Lime 2*873          3'812          6'696 

Magnesia 25'091        24'251        21'744 

Soda 0-274 


100-049   100-097    99*595 

One  of  the  essential  constituents  of  the  andesite  and  tufa 
rocks  of  Buffalo  Peaks,  Mosquito  Range. 

PYROXENE. 

Monoclinic ;  primary  form  an  oblique  rhombic  prism ;  generally  occurs  in 
short,  thick  crystals,  and  often  in  twins  ;  also  amorphous,  coarsely  lami- 
nar, granular  and  fibrous,  fibres  often  fine  and  long.  Lustre  vitreous  in- 
clining to  resinous,  ^sometimes-  pearly.  Color  green  of  various  shades, 
verging  on  one  side  to  white  or  grayish-white,  and  on  the  other  to  brown 
or  black,  Streak  white  to  gray  and  grayish-green.  Fracture  conchoidal, 
uneven.  Brittle.  H.  5—6.  G.  3'23 — 3'5.  Composition :  Bisilicate  of 
various  bases,  the  bases  being  lime,  magnesia,  protoxide  of  iron,  protoxide 
of  manganese,  and  sometimes  potash  and  soda. 

Next  to  the  feldspars,  pyroxene  is  the  most  universal  con- 
stituent of  the  igneous  rocks  of  the  mountains. 

PYROI*USITE.     Gray  Oxide  of  Manganese. 

Orthorhombic;  occurs  crystallized,  but  generally  in  botryoidal  and  reni- 
form  masses,  with  a  radiating,  fibrous  or  columnar  structure  ;  or  in  granu- 
lar masses.  Often  soils.  Lustre  metallic.  Color  iron-black,  dark  steel- 
gray,  sometimes  bluish.  Streak  black  or  bluish-black,  sametimes  subme- 
tallic.  Rather  brittle.  H.  2— 5'5.  G.  4'82.  Composition  : 

Manganese  63'3 

Oxigen 36'7 


100-00 

Peale  mentions  its  occurrence  on  Silver  Heels  Mountain, 
near  Fairplay,  and  in  the  San  Juan  country. 


Orthorhombic;  primary  form  a  right  rhombic  prism;  occasionally  hemi- 
hedial;  occurs  in  columnar  crystals  striated  vertically  ;  also  fibrous  and 
massive,  or  radiating;  sometimes  granular.  Lustre  submetallic.  Color 
dark  steel-gray,  iron-black.  Streak  reddish-brown,  sometimes  nearly 
black.  Opaque  ;  minute  splinters  sometimes  brown  by  transmitted  light. 
Fracture  uneven.  H.  4.  G.  4'2  —  4'4,  Composition  : 

Sesquioxide  of  Manganese  ......  89"8 

Water  .................................  10'2 


100-0 

W.  B.  Smith  reports  its  occurrence  in  small  masses  in  the 
region  of  Devil's  Head  Mountain,  Douglas  County. 


APPENDIX.  6l 

ARGENXOBISMUXIXE. 

F.  A.  Genth  gives  the  following  analysis  of  argentobismutite  from  Lake 
City,  Hiusdale  County  : 

Sulphur  .............................  16.66 

Bismuth  .............................  52.89 

Silver   ..............................  26.39 

Lead  ................................     406—100.00 


Antimonial  Lead  Ore. 
Orthorhombic;  occurs  crystallized  in  modified  rectangular  prisms,  often 
cruciform  or  compounded  into  shapes  like  a  cog-wheel.  Also  massive, 
granular  compact.  Lustre  metallic.  Color  and  slreak  steel-gray,  inclin- 
ing to  blackish  lead  gray  or  iron  black.  Opaque.  Fracture  conchoidal  or 
uneven.  Brittle.  H.  2.5  —  3.  G.  5.7  —  5.9.  Composition: 

Sulphur  ..............................   19.7 

Antimony  ...........................  25.0 

Lead  .....  .*  .............................  42.4 

Copper  ..............................  12.9—100.00 

M.  C.  Ihlseng  mentions  the  common  occurrence  of  this  min- 
eral in  the  lodes  of  Bear  and  Anvil  Mountains,  San  Juan 
County.  Its  associate  mineral  is  galena. 


Asbestus  (p.  30)  of  an  olive-green  color.     Fibres  usually  coarse  and  stiff. 

Needle-like  fibres  an  inch  or  more  in  length  in  clear  quartz 
crystals  near  Calumet,  Chaffee  County. 


A  natural  alloy  of  gold  and  silver  in  the  proportion  of  two  of  gold  to  one 

of  silver,  or, 

Gold  ....................................  65 

Silver  .........  .  ........  .  ................  35—100 

Color  pale   yellow  to  yellowish-white.     Known  crystals  tabular,  and  im- 

perfect cubes.     G.  14  to  17. 

According  to  P.  H.  VanDiest  the  ore  in  the  Nelly  mine, 
San  Miguel  County,  is  crystallized  electrum. 


Copperas.     Green  Vitriol.     Sulphate  of  Iron. 
Monoclinic;  in  acute  rhombic  prisms.     Occurs  massive,  pulverulent,  bo- 
tryoidal,  reniform,  stalactitic   and   crystallized.     Lustre   vitreous.     Color 
various  shades  of  green,  passing  into  white;    becoming  yellowish-white  on 
exposure.     Subtransjtarent  to  translucent.     Taste  sweetish,  astringent,  and 
metallic.     Fracture  conchoidal.     Brittle.     H.2.     G.  1.832.     Composition: 
Sulphuric  Acid  .....................   28.8 

Protoxyd  ol  Iron  ..................  25.9 

Water.".  ...............................  45.3—100.0 

Proceeds  from  the  decomposition  of  pyrite  in  the  Black 
Iron  and  other  mines  around  Red  Cliff;  clear  green  crystals 
and  large  masses.  Crystals  and  small  masses  in  the  Pennsyl- 
vania mine,  Peru  District,  Summit  County. 

NATIVE    CHARCOAL,. 

F.  F.  Chishelm  mentions  the  occurrence  of  native  charcoal 
in  considerable  quantities  in  the  anthracite  on  the  head  of 
Elk  Head  Creek  in  Routt  County.  According  to  Chisolm  it 
is  of  common  occurrence  in  Colorado  lignites.  Charcoal  is 
found  at  various  depths  in  the  Bassick  mine,  Custer  County. 


62  APPENDIX. 

AMJNITB.     Alumstone. 

Khornbohedral  ;  crystals  modifications  of  an  obtuse  rhomboid.  Massive, 
having  a  fibrous,  granular,  or  impalpable  texture.  Lustre  of  crystals  vit- 
reous, or  a  little  pearly  on  the  basal  plane.  Color  white,  grayish  or  red- 
dish. Streak  white.  Transparent  —  subtranslucent.  Fracture,  flat  conch- 
oidal,  uneven  ;  of  massive  varieties  splintery  ;  sometimes  earthy.  Brittle. 
H.  3  5—4.  G.  2.58—2-752.  Composition  :  " 

Sulphuric  Acid  ...................  38.53 

Alumina  ...........................  37.13 

Potash  ..............................  11.34 

Water  ................................  13.00—100.00 

S.  F.  Emmons  mentions  its  occurrence  in  the  Iron  mine  at 
Leadville.  Probably  occurs  at  a  number  of  places  along  the 
foot-hills  with  native  alum. 

SIDEROPHYULITE.     (New).     Black   Mica.     If.  C.  Lewis,  Proc.  Ac. 

Nat.  Sc  Phila.,  1880. 

Color  black;  by  transmitted  light  chrome  green.     Brittle.     Analysis: 
Silica  ................................  36.68 

Alumina  ...........................  20.41 

Sesquioxyd  of  Iron    .............     1.55 

Protoxyd  of  Iron  .................  25.50 

Protoxyd  of  Manganese  ........     2.10 

Magnesia  ...........................     1.14 

Lime  .................................     0.81 

Soda   ................................     1.09 

Lithia  ..............................     0.37 

Potassa  ..............................     9.20 

Water  ...............................     1.01—99.86 

Found  in  the  Pike's  Peak  region. 


(New).     Telluride  of  Iron.     C.  U.  Shepard,  Contri- 
butions to  Mineralogy,  1877. 
Color  silver-white.     Analysis  by  Edmond  Fuchs  : 

Gold   ..............................     5.228 

Silver   .............................     4.198 

Tellurium  ........................  19.650 

Iron  ................................  70.624 

Sulphur  ...........................     trace—  99.700 

Occurs  in  the  Grand  View  and  Phil  Sheridan  mines,  Sun- 
shine, Boulder  County. 

URACOXIXE.     Sulphate  of  Uranium. 

Amorphous,  earthy,  or  scaly,  and  of  fine  lemon-yellow  color,  or  orange. 
Composition  : 

Sulphuric  Acid  ....................  10.16 

Sesquioxyd  of  Uranium  ........  66.05 

Sesquioxyd  of  Iron  ..............  0.86 

Lime  .................................  2.62 

Water  ................................  20.06—99.76 

In  the  Wood  lode,  Leavenworth  Gulch,  near  Central  City, 
with  pitchblende. 

STIBNITE  (p.  23).  —  Large  veins  ol  sulphide  of  antimony  be- 
tween Troublesome  Creek  and  Lost  Lake  in  Grand  County. 
Float  masses  of  stibnite  and  quartz  are  found  two  or  more  feet 
in  thickness. 


APPENDIX.  63 

ANGLESITE  (p.  7). — Occurs  as  the  oxidation  product  of 
galena  in  the  mines  around  Red  Cliff.  It  is  abundant  in  the 
form  of  minute  crystals,  or  "sand." — Emmons. 

ANTHRACITE  (p.  47). — True  anthracite  is  found  on  the  head 
of  Elk  Head  Creek  in  Routt  Co.  F.  F.  Chisolm,  who  exam- 
ined the  field,  says  there  are  three  veins,  the  upper  four  feet 
thick,  the  second  three  and  one  half  feet  and  the  third  one 
foot  in  thickness.  Analyses  from  the  two  upper  veins  : 

Sulphur  0.79  0.44 

Moisture 1,02  2.50 

Volatile  matter 9.66  3.20 

Fixed  Carbon  83.50  88.20 

Ash 5.82  6.10 

CALAMINE  v.  27). — Abundant  and  crystallized  in  the  Sun- 
nyside  mine,  San  Juan  County. — Ihlseng. 

GADOLINITE. — Massive  in  the  upper  canon  of  the  South 
Platte  River. 

JAROSITE  (p.  7). — Minute  but  perfect  crystals  in  the  Black 
Iron  mine  near  Red  Cliff. — Emmons. 

LIMONITE  (p.  33). — Pseudomorphs  after  pyrite  in  the  Nelly 
mine,  San  Miguel  County. 

MOLYBDENITE  (p.  25). — Common  in  the  lodes  on  Cement 
Creek  and  near  Chattanooga,  San  Juan  County. — Ihlseng. 

PHENACITE  (p.  7). — Occurs  in  prismatic  crystals  on  aqua- 
marine on  Mt.  Antero  in  Chaffee  County,  and  is  thought  to 
be  the  decomposition  product  of  beryl. 

RUTILE  (p.  58).— W.  B.  Smith  found  black  ferriferous 
rutile  on  St.  Peter's  Dome,  El  Paso  County. 

GARNET  (p.  33. ) — Dr.  Konig  publishes  the  following  analy- 
sis of  a  massive  titaniferous  garnet  from  southern  Colorado, 
and  comments  on  its  relation  to  schorl omite: 

Silica 30-71 

Titanic  Acid 8'11 

Alumina  2'20 

Sesquioxide  of  Iron 23'20 

Lime 31 '40 

Magnesia T22 

Protoxide  of  Manganese 0' 46— 99.98 

PYRITE  (p.  42) — Octahedral  crystals  on  Mount  Richard 
Owen,  Anthracite  Creek,  Gunnison  County. 

CHRYSOCOLLA  (p.  29). — Occurs  near  Pine  Grove,  in  Platte 
Canon,  associated  with  red  oxide  of  copper. 

BISMUTHINITE  (p.  9). — Occurs  in  the  mines  of  San  Juan 
County. 


64  0  APPENDIX. 

CORUNDUM.     Emery.     Blue,  Sapphire.     Red,  Ruby. 

Rhornbohedral ;  commonly  occurs  crystallized  in  six-sided  prisms  ;  also  in 
obtuse  and  acute  hexahedral  pyramids;  cleavage  basal,  sometimes  perfect, 
but  interrupted.  Also  massive,  granular  or  impalpable.  Lustre  vilreous, 
sometimes  pearly  in  the  basal  planes,  and  occasionally  exhibiting  a  bright 
opalescent  star  of  six  rays  in  the  direction  of  the  axis  (asteriated  sapphire). 
Color  blue,  red,  yellow,  brown,  gray  and  nearly  white.  Transparent  to 
translucent.  Fracture  conchoidal.  Exceedingly  tough  when  compact. 
H.  9.  G.  3.909 — 4.19.  Composition,  pure  alumina: 

Oxygen  46.6 

Aluminum  53.4—100.0 

W.  B.  Smith  mentions  the  occurrence  of  a  corundum  shist 
in  ChafFee  County  which  contains  35  per  cent  of  corundum. 
It  occurs  in  thin  flat  crystals,_  and  many  of  them  are  true  sap- 
phires. 

SAPPHIRE.     Blue  Corundum. 
The  blue  variety  of  corundum. 

Thin  flat  crystals,  the  largest  not  more  than  5mm  in  diam- 
eter, are  quite  abundant  in  the  corundum  shist  from  Chaffee 
County.  The  crystals  are  transparent  and  true  sapphires. 

PI^AGIOCI^ASE.     Triclinic  Feldspar. 

The  name  for  the  group  of  triclinic  feldspars,  the  two  prominent  cleavage 
directions  of  which  are  oblique  to  one  another. 

The  most  abundant  constituent  of  the  andesite  of  Buffalo 
Peaks. — W.  Cross. 

XMENARDIXE.     Anhydrous  Sulphate  of  Soda. 

Orthorhombic:  cleavage  basal;  primary  form  a  right  rhombic  prism. 
Occurs  in  rhombic  octahedrons,  simple  or  modified  on  the  summit,  aggre- 
gated in  crusts  and  druses.  Color  white.  Translucent  or  pellucid.  Lus- 
tre vitreous.  Effloresces  and  becomes  covered  on  the  surface  with  a  white 
powder  on  exposure  to  the  air.  Taste  saline.  Wholly  soluble  in  distilled 
water.  Refracts  doubly.  H.  2.5.  G.  2.6—2.73.  Analysis : 

Water  and  organic  matter 19.10 

Silica 5.20 

Alumina  and  oxide  of  iron  14.40 

Chlorine  2.40 

Sulphuric  Acid 25.80 

Lime 8.80 

Magnesia 3.90 

Soda  19.10—98.70 

Occurs  in  quantity  at  Burdsall's  Lake  near  Morrison. 

ZIRCON  (p.  58). — Small  crystals  in  the  porphyrite  of  Ten- 
Mile  District,  Summit  County.  —  W.  Cross. 

POLYBASITE  (p.  43). — The  distinguishing  silver  ore  of  Up- 
per San  Miguel  District  and  Marshal  Basin,  San  Miguel 
County.  — Ihlseng. 

ASBESTUS  (p.  30). — Beautiful  snow-white  asbestus  is  found 
near  Jasper,  Rio  Grande  County.  Asbestus  is  also  found  in 
float  rock  on  Arapahoe  Peak. 


APPENDIX.  ^  65 

DYSCRASIXB.     Antimonial  Silver. 

Orthorhombic ;  occurs  in  hexagonal  prisms  and  stellate  forms  ;  also  mass- 
ive, disseminated,  or  in  grains.  Color  and  streak  between  silver-white  and 
tin-white,  often  tarnished  yellow  or  reddish.  Lustre  metallic.  Easily 
frangible.  Soft  and  slightly  malleable.  H.  3.5 — 4.  G.  9.44 — 9.82.  Comp.: 

Silver  78 

Antimony  22 — 100 

Hills  and  Endlich  mention  the  occurrence  of  dyscrasite  in 
the  mines  of  Poughkeepsie  Gulch,  San  Juan  county. 

MYDROPMA^B.     Variety  of  Opal. 

Massive,  amorphous.  Lustre  vitreous,  frequently  subvitreous.  Translu- 
cent. Color  whitish,  or  light  colored.  Adheres  to  the  tongue  and  becomes 
more  translucent  or  transparent  in  water.  Composition  : 

Silica 93.00 

Alumina 2.00 

Water  5.00—100.00 

A  white  and  nearly  opaque  variety  of  hydrophane,  in 
rounded  lumps,  with  a  white  chalky  or  glazed  coating,  is 
found  in  the  State,  but  the  locality  is  a  secret.  When  water 
is  dropped  upon  it,  it  first  becomes  very  white  and  chalky, 
and  then  gradually  perfectly  transparent.  This  property  is 
developed  so  strikingly  that  the  name  "Magic  Stone"  has 
been  proposed  for  it,  and  its  use  suggested  in  rings,  lockets, 
charms,  etc.,  to  ^conceal  photographs,  hair  or  other  objects 
which  the  wearer  wishes  to  reveal  only  when  his  caprice 
dictates  (Kunz\ 

R.IO1SITB.     Bismuth-Tetrahedrite. 

Has  a  conchoidal  fracture,  an  iron-black  color,  black  streak  and  greasy- 
metallic  lustre.  An  analysis  of  the  Switzerland  mineral  gave  : 

Sulphur 29'IQ 

Arsenic  11'44 

Antimony  2'19 

Bismuth 13'07 

Copper  37'52 

Silver  0'04 

Iron 6-51 

Cobalt  1-20— 101-07 

Abundant  in  the  Yankee  Girl  mine,  Ouray  county,  carrying 
about,  two  per  cent  of  silver. 

ZOR.GI'TB*     Seleniuret  of  Lead  and  Copper. 

Massive,  granular.  Lustre  metallic.  Color  dark  or  light  lead-gray,  some- 
times inclining  to  reddish,  and  often  with  a  brass-yellow  or  blue  tarnish. 
Streak  darker.  Brittle.  H.  2'5.  G.  7 — 7 '6.  Composition  : 

Selenium  34 

Lead 50 

Copper 15 

Silver 1—100 

Occurs  in  quantity  in  the  Pearl  lode,  Minnesota  gulch,  San 
Juan  county. 


66          t  APPENDIX. 

RuTiLE  (p.  58). — Small  jet-black  tetragonal  crystals  occur 
in  quartz  gangue  near  the  Eureka  tunnel,  St.  Peter's  Dome, 
El  Paso  county,  associated  with  arfvedsonate  and  zircon,  and 
closely  resembling  in  form  the  latter  mineral.  An  analysis 
by  Eakins  gave  : 

Titanic  Acid 9473 

Oxyd  of  Iron 3'77 

Silica 1-37 

Water 0'71— 10078 

SCHIRMERITE  (p.  32). — In  the  Santa  Cruz  mine,  Howard's 
Fork,  San  Miguel  county,  with  bismuthinite,  chalcopyrite 
and  galena. 

EPIDOTE  (p.  36). — Good  single  crystals  are  found  near  the 
Colorado  Coal  and  Iron  Go's  mine  at  Calumet. 

ANGLESITE  (p.  7). — L,arge  masses  in  the  Madonna  mine, 
Chaffee  county,  often  as  pseudomorph  after  galena. 

ARSENOPYRITE  (p.  40). — Near  Ruby  camp,  Gunnison  coun- 
ty. On  Mount  Wilson,  San  Miguel  county.  . 

BORNITE  (p.  14). — In  the  Plutus  mine,  Idaho  Springs.  In 
the  mines  of  Red  Mountain  district,  San  Juan  and  Ouray 
counties.  Near  Maysville,  Chaffee  county.  Gem  mine,  Fre- 
mont county,  with  niccolite. 

CHALCOCITE  (p.  37). — Occurs  almost  alone,  in  sandstone 
with  matrix  of  calcite,  in  San  Miguel  county.  Massive  at 
Ironton,  Ouray  county. 

HEMATITE  (p.  34). — Large,  irregular  deposit  in  the  Breece 
mine,  Leadville.  Large  beds  near  Ashcroft  and  Carbondale, 
Pitkin  county. 

STROMEYERITE  (p.  57). — Rarely  in  the  Plutus  mine,  Idaho 
Springs.  In  quantity  in  the  Yankee  Girl  mine,  Ouray  Co. 

TENNANTITE  (p.  8). — Frank  Hough  mine,  Hinsdale  Co. 

GRAPHITE  (p.  27). — In  quartz  veins  2^2  feet  thick  on 
branches  of  Quartz  Creek,  Gunnison  county. 

MAGNETITE  (p.  34). — Grayback  gulch,  Costilla  county. 
Titaniferous  variety  on  Iron  mountain,  Fremont  county. 
Both  worked  by  the  Colorado  Coal  and  Iron  Company.  A 
pure  magnetite  in  large  quantity  on  Cebolla  Creek,  and  titan- 
iferous  magnetite  near  Snowmass  mountain,  Gunnison  county. 
In  quantity  near  Hamilton,  Park  county.  Near  Ashcroft  and 
Carbondale,  Pitkin  county. 

AcTiNOUTE  (p.  30). — Light  green  and  bluish  green  actino- 
lite  is  found  on  Mt.  Ouray,  Chaffee  County. 


APPENDIX.  67 

NATIVE  SULPHUR  (p.  6). — In  the  Queen  of  the  West  mine, 
Peru  District,  Summit  County,  with  alabandite  and  rhodo- 
chrosite.  In  the  S.  S.  mines,  Park  County.  In  Routt  Co., 
but  the  exact  locality  is  not  known.  In  the  Mineral  Chief 
lode,  Georgetown,  with  galena. 

RHODOCHROSITE  (p.  10). — Rich  red,  transparent  crystals 
in  the  John  Reed  mine  at  Alicante,  Lake  county.  Some 
cleavage  pieces  are  as  pellucid  as  Iceland  spar  and  show  the 
same  strong  double  refraction.  It  also  occurs  opaque,  mass- 
ive and  cleavable,  enclosing  bright  cubic  crystals  of  pyrite. 
Analysis  by  James  B.  Macintosh  gave  : 

Protoxyd  of  Manganese 58.325 

Protoxyd  of  Iron 3.615 

Carbonic  Acid  (by  difference) 38.06  —100.00 

At  the  Ule  mine,  Lake  City,  opaque  flesh-colored  crystals, 
rounded  and  curved  like  dolomite,  are  found  on  galena. 
Large  masses  of  white,  yellowish  and  light  pink  color  as 
stalagmites  in  the  Stevens  mine,  near  Gray's  Peak. 

HYALITE  (p.  41). — Crusts  on  the  hypersthene-andesite  of 
Buffalo  Peaks,  Chaffee  county. 

SCHEELITE  (p.  27). — In  crystals  in  some  of  the  mines  of 
Baker  Park,  San  Juan  county. — (EndlicJi). 

CUPRITE  (p.  40). — Sweet  Home  mine,  Buckskin,  Park  Co. 
North  Fork  of  the  Poudre,  Larimer  county,  with  native  cop- 
per and  chalcocite. 

CELESTITE  (p.  25). — On  Apishapa  Creek. 
HESSITE  (p.  28). — Mines  of  Red  Cliff,  Eagle  county.     Oc- 
casionally met  with  in  the  mines  of  La  Plata  county. 

PETZITE  (p.  43). — Hotchkiss  mine,  Hinsdale  county. 

SYLVANITE  (p.  32). — In  quartz  veins  on  Junction  Creek, 
and  at  the  head  of  the  Rio  la  Plata,  La  Plata  county. 

APOPHYLLITE  (p.  15). — Endlich  mentions  its  occurrence  on 
Hunt's  Peak,  Fremont  county. 

BISMUTHENITE  (p.  9). — Near  Silverton,  in  long  steel-blue 
and  iridescent  needles,  associated  with  hubnerite,  tetrahedrite 
and  drusy  quartz. 

OPAL  (p.  40). — Nodules  of  milk-white  opal,  some  having 
moss-like  markings,  on  Badger  Creek,  South  Park. 

FLUORITE  (p.  10). — In  veins  with  quartz  in  Poughkeepsie 
gulch,  San  Juan  county.  On  Kelso  mountain,  Clear  Creek 
county. 

CHRYSOCOLLA  (p.  29).— In  the  Sangre  de  Christo  moun- 
tains, Custer  and  Saguache  counties. 


68  APPENDIX. 


Penjield,  Am.  Jr.  Sc.t  July,  1888. 
Monoclinic  ;  crystals  generally  tabular  in  habit,  transparent,  colorless  or 
slightly   yellowish.     Lustre   vitreous.     H.  6  —  7.     G.  2'598.     Analysis  of 
Colorado  mineral  gave  : 

Silica  ....................  .............  51.8 

Glucina  ...  ...........................  39.6 

Lime  .................................     1.0 

Water  ................................     8.4—100.8 

Found  on  Mt.  Antero,  Chaffee  county,  with  phenacite,  or- 
thoclase,  beryl,  muscovite  and  fluorite.  Occurs  in  small  thin 
rectangular  blades  attached  to  quartz,  and  having  the  shape  of 
a  thin  slice  cut  from  the  side  of  a  cylinder  parallel  to  its  axis. 

PYRR.HOXIXE.     Magnetic  Iron  Pyrites. 

Hexagonal  ;  commonly  massive  and  amorphous  ;  structure  granular.   Lus- 
tre metallic.     Color  between  bronze-yellow  and  copper-  red,  and  subject  to 
speedy   tarnish.     Streak   dark   grayish-black.     Brittle.     Magnetic,  being 
attractable  in  fine  powder  by  a  magnet,  eyen  when  not  affecting  an  ordi- 
nary needle.     H.  3'5  —  4'5.     G.  4'4  —  4.68.     Composition  : 
Sulphur  ..............................  39'5 

Iron  ...................................  60-5—  100-0 

Occurs  in  small  quantity  in  the  lodes  of  Needle  mountains, 
San  Juan  county. 

SPHBROSIDBRITB.     Concretionary  Siderite.     Carbonate  of  Iron. 

In  globnlar  concretions,  either  solid  or  concentric  scaly,  with   usually  a 

fibrous  structure.     Composition  : 

Carbonic  Acid  .......................  37'9 

Protoxyd  of  Iron.-  ................  62'1  —  lOO'O 

A  thin  seam  of  spherosiderite  occurs  above  the  coal  of  the 
Laramie  formation  in  many  parts  of  the  state.  In  some  places 
it  has  weathered  out  in  nodules,  which  are  found  upon  the 
plains  in  great  quantity.  It  is  found  near  Trinidad  and  El 
Moro  in  Las  Animas  county,  Walsenburgh  in  Huerfano  coun- 
ty, and  Marshall  in  Boulder  county. 

H  VmtOPIIAXK.     Variety  of  Opal. 

Massive,  amorphous.     Lustre  vitreous,  frequently  subvitreous.     Translu- 
cent.   Color  whitish,  or  light  colored.    Adheres  to  the  tongue  and  becomes 
more  translucent  or  transparent  in  water.     Composition  : 
Silica  ..........................................     93.00 

Alumina  ......................................       2.00 

Water  .........................................       5.00—100.00 

A  white  and  nearly  opaque  variety  of  hydrophane,  in 
rounded  lumps,  with  a  white  chalky  or  glazed  coating,  is 
found  in  the  State,  but  the  locality  is  a  secret.  When  water 
is  dropped  upon  it,  it  first  becomes  very  white  and  chalky, 
and  then  gradually  perfectly  transparent.  This  property  is 
developed  so  strikingly  that  the  name  uMagic  Stone"  has 
been  proposed  for  it,  and  its  use  suggested  in  rings,  lockets, 
charms,  etc.,  to  conceal  photographs,  hair  or  other  objects 
which  the  wearer  wishes  to  reveal  only  when  his  caprice 
dictates  (Kunz\ 


APPENDIX.  69 

SAMARSKIXB.     Hillebrand,  Proc.  Col  Sc.  Soc,,  1888. 

Orthorhornbic.     Lustre  of  surface   of  fracture   shining   and    submetallic. 

Color  velvet-black.     Streak  dark  reddish-brown.     Opaque.     Fracture  sub- 

conchoidal.     H.  5.5—6.     G.  5.614—5.69. 

Occurs  in  granitic  debris  on  Devil's  Head  Mountain,  Dong- 
las  County,  in  fragments  of  all  sizes  up  to  that  of  a  chestnut, 
without  crystal  form.  The  following  analysis  by  Hillebrand 
shows  the  composition: 

Tantalic  Acid 27.03 

Columbic  Acid 27.77 

Tungstic  Acid 2.25 

Oxide  of  Tin 0.95 

Zifconia 2.29 

Protoxyd  of  Uranium 4.02 

Thoria 3.64 

Protoxyd  of  Cerium 0.54 

Oxide  of  Didymium  and  Lanthanum...  1.80 

Oxide  of  Erbium 10.71 

Yttria 6.41 

Sesquloxyd  of  Iron 8.77 

Protoxyd  of  Iron 0.32 

Protoxyd  of  Manganese 0.78 

Zirconia 0.05 

Oxide  of  Lead 0.72 

Lime 0.27 

Potassa 0.17 

S'-da  and  Lithia 0.25 

Water  1.58 


100.31 
MEGABASITE.      Tungstate  of  Manganese. 

Orthorhombic ;  usually  occurs  in  fine  needles.  Lustre  vitreous,  a  little 
adamantine.  Color  brownish-red,  clover- brown  to  yellowish-brown,  with 
a  reddish-brown  to  hyacinth-red  translucency.  Streak  pale  yellowish- 
brown  to  ochre-yellow.  H.  3.5 — 4.  G.  6.45. 

H.  F.   Keller  gives  the  following  analysis  of  megabasite 
from  Bonita  Mountain,  near  Silverton: 

Tungstic  Acid 74.24 

Oxide  of  Manganese 21.09 

Protoxyd  of  Iron 2.06 

Oxide  of  Copper 0.11 

Oxide  of  Manganese trace. 

Silica 2.13 


99.63 

Lime-Aluminagarnet. 
A  cinnamon-colored  variety  of  garnet.     Composition  : 

Silica 41 

Alumina 23 

Oxide  of  Iron 4 

Lime  32—100 

Longfellow  gulch,  ChafFee  county,  in  dark  rhombic  dodeca- 
hedrons, disseminated  through  chloritic  schist.  In  metamor- 
phosed limestone  near  Calumet.  They  have  finely  polished 
faces  and  beautiful  clear  color. 


70  APPENDIX. 

WARREBJIXE.    (New.)    Sulphantimonate  of  Lead.     L.  G.  Eakins,  Proc- 

Col.  Sc.  Soc.,  1888. 

Small  acicular  crystals  forming  matted  wooly-like  masses.      Color  grayish- 

black,  occasionally  iridescent.     Analysis  by  Eakins: 

Lead  ............................................  39.33 

Antimony  ......................................  36.34 

Iron  .............................................     1.77 

Silver,  Copper,  Manganese  .-  .............  trace. 

Sulphur  ..............  ..........................  21.19 

Insoluble  gangue  ..............................  52 

99.15 

Found  in  the  Domingo  lode,  on  the  ridge  between  Canon 
and  Baxter  Basin,  Gunnison  county.  Named  after  E.  R. 
Warren  of  Crested  Butte. 


Sulphuret  of  Silver  and    Antimony.     Eakins, 
Proc.  Col.  Sc.  Soc.,  1888. 

Monoclinic;  occurs  in  small,  deeply  striated  prisms.  Lustre  metallic. 
Color  and  streak  light  steel  gray,  inclining  to  silver  white,  also  blackish 
lead  gray.  Yields  easily  to  the  knife,  and  is  rather  brittle.  Fracture  sub- 
conchoidal  —  uneven.  H.  2  —  2.5.  G.  6  —  6.4.  Comp.:  Sulphur  18.6,  anti- 
mony 25.9,  lead  31.2,  silver  24.3.  —  100.  Silver  often  replaced  by  lead. 

Occurs  in  a  mine  on  Augusta  Mountain,  Gunnison  Co.  ,  in 
silicious  gangue  together  with  pyrite  and  sphalerite,  and 
forms  groups  of  acicular  crystals  which  are  elongated  prisms, 
deeply  striated,  but  too  small  to  be  measured.  The  analysis 
is  as  follows: 

Silver....:  ......................................  .  trace. 

Lead  .............................................  55.52 

Iron  .............................................  trace. 

Antimony  .................  .  ....................  25.99 

Sulphur  (calculated)  ........................  J8.98 

100.40 

ENARGITE  (p.  13).  —  In  the  mines  of  Summit  district,  Rio 
Grande  county. 

JET  (p.  45).  —  On  the  Trinchera  mesa,  southeast  Colorado. 

Moss  AGATE  (p.  18).  —  In  nodules  on  Badger  Creek,  South 
Park. 

ORTHOCLASE  (p.  12).  —  Excellent  crystals  are  found  in  the 
slide  rock  just  above  the  river  on  Crested  Butte  Mountain, 
Gunnison  County. 

AMETHYST  (p.  23).  —  Pale  colored  amethyst  is  found  on  Car- 
nero  Creek,  Saguache  County.  In  form  they  are  quite  re- 
markable, the  prismatic  faces  being  enormously  large,  while 
the  terminal  pyramidal  faces  are  very  minute.  "Phantom 
crystals"  are  often  enclosed,  and  occasionally  liquid  inclu- 
sions with  movable  bubbles. 


CLEAR   CREEK   COUNTY   MINERALS. 


Clear  Creek  County  is  pre-eminently  mineral-bearing,  the 
only  tillable  land  being  a  few  rods  in  width  along  the  streams. 
The  southeastern  portion  of  the  county,  however,  is  valuable 
only  for  timber,  as  mineral  veins  in  that  region  either  do  not 
exist  or  have  not  been  discovered.  The  formation  is  archean, 
veined  with  dikes  of  eruptive  rocks,  in  which  porphyry  pre- 
dominates. Heavy-bedded  and  thinly-laminated  gneiss,  red 
and  gray  granite,  schist,  syenite,  felsitic  and  hornblendic 
rocks  pass  by  imperceptible  phases  from  one  to  the  other  in 
inextricable  confusion,  and  the  dip  of  the  rocks  are  as  variable 
as  their  structural  character. 

It  is  somewhat  remarkable  that  so  few  accessory  minerals 
have  been  found  in  the  granite  and  kindred  rocks,  and  equal- 
ly remarkable  that  the  minerals  found  in  the  veins  are  locally 
few  in  variety  and  seldom  crystallized.  Taken  as  a  whole, 
however,  Colorado  is  probably  the  richest  in  variety  of  min- 
erals of  any  known  region.  But  the  number  of  local  miner- 
als might  be  materially  increased  were  the  finders  as  much 
interested  in  learning  the  nature  of  the  minerals  that  pass 
through  their  hands  as  in  determining  their  gold  and  silver 
value.  The  following  minerals  are  found  in  Clear  Creek 
Coiinty  : 

Acanthite  (orthorhombic  silver  glance).  —  A  few  small 
crystals  were  found  in  a  lot  of  polybasite  crystals  from  the 
Emma  mine. 

Albite  (soda  feldspar). — A  constituent  of  some  of  the  gran- 
itic rocks,  particularly  on  Fall  River. 

Amethyst.— r-A  few  specimens  of  good  color  have  been 
found  in  a  lode  near  Dumont  and  on  Chicago  Creek. 

Anglesite  (sulphate  of  lead). — Aggregations  of  small  crys- 
tals in  the  Freeland  mine.  Small  crystalline  masses  in  the 
Troy  mine,  Georgetown,  intimately  associated  with  cerussite. 

Aragonite  (carbonate  of  lime). — Large  beautiful  specimens 
of  coralloidal  form  were  found  in  the  Marshall  tunnel  a  num- 
ber of  years  ago.  A  shaft  near  the  Argentine  lode,  on  Leav- 
enworth  Mountain,  furnishes  yellow  tinted  specimens. 


2  Clear  Creek  County  Minerals. 

Argentite  (silver  glance). — In  small  quantities  in  nearly 
all  the  silver  mines.  Masses  weighing  two  to  three  pounds 
have  been  found  in  the  Colorado  Central  and  Saxon  mines. 
Crystals  rare  and  quite  .small. 

Arsenopyrite  (arsenical  pyrites). — Occasionally  found  in 
the  veins  about  Empire,  Idaho  and  in  Geneva  District. 

Autunite  (phosphate  of  uranium  and  lime). — Small  green- 
ish-yellow tabular  crystals  in  the  Peabody  lode,  near  George- 
town, and  in  a  lode  on  Chicago  Creek. 

Azurite  (blue  carbonate  of  copper.) — Occurs  as  an  incrus- 
tation near  the  surface  of  many  of  the  lodes. 

Barite  (heavy  spar). — Of  frequent  occurrence  in  some  of 
the  veins.  Clusters  of  amber-colored  crystals  in  the  7:30 
mine.  In  the  Little  Giant  mine  in  thin  white  crystals.  Small 
tabular  crystals  in  the  Oneida  and  many  other  lodes. 

Biotite  (black  mica). — A  constituent  of  much  of  the  gran- 
ite and  eruptive  rocks.  • 

Bornite  (purple  copper  ore). — Of  frequent  occurrence  in  the 
gold  mines.  Handsome  specimens  in  the  Neath. 

Calcite  (carbonate  of  lime). — Occurs  in  small  quantities 
in  many  of  the  mines.  Nail-head  crystals  in  the  Terrible. 

Cerargyrite  (horn  silver,  chloride  of  silver.) — Thin  crusts 
on  the  surface  ores  from  some  of  the  lodes  on  Democrat  and 
Lincoln  Mountains. 

Chalcanthite  (blue  vitriol). — Forms  on  the  walls  of  the 
Whale  Tunnel,  near  Idaho. 

Chalcedony. — Beautiful  botryoidal  specimens  have  been 
found  in  the  mines  at  Idaho.  Occasionally  met  with  in  the 
Little  Giant  and  other  veins. 

Chalcopyrite  (copper  pyrites). — Of  general  occurrence  but 
in  less  quantity  than  pyrite,  and  carries  more  gold  and 
silver.  A  few  fine  crystals.,  usually  studded  with  minute  crys- 
tals of  tennantite,  have  been  found  in  the  Freeland  mine. 

Chrysocolla  (silicate  of  copper). — In  the  Champion  lode, 
near  Idaho. 

Dolomite  (magnesian  limestone). — Of  frequent  occurrence 
in  the  veins  in  Ohio  District.  Occasionally  found  in  other 
lodes. 

Enargite  (arsenical  sulphide  of  copper). — A  small  amount 
is  found  in  the  surface  ores  of  the  Centennial  mine,  associated 
with  native  copper. 


Clear  Creek  County  Minerals.  j 

Epidote.  —  Massive  and  crystallized  in  the  granitic  rocks 
between  Georgetown  and  Green  Lake.  Very  good  crystal  on 
Floyd  Hill. 

Fibrolite.  —  Inferior  fibrolite  of  a  grayish-green  color  oc- 
curs in  the  granite  on  Sherman  Mountain. 

Fire  Opal.  —  A  very  handsome  opal  showing  bluish  and 
yellowish  flames,  and  greatly  resembling  sofhe  Mexican  opals, 
is  found  in  a  felsite  rock  in  Gilson  Gulch,  near  Idaho. 

Fluorite  (fluor  spar).  —  Impure  massive  fluorite  of  deep 
purple  color  is  found  in  some  of  the  lodes  on  McCJellan  Mt. 

Galenite.  —  The  most  abundant  mineral  in  the  silver  mines. 
Good  crystals  in  the  Dunderberg,  Terrible  and  Little  Giant 
mines.  In  many  of  the  mines  it  occurs  in  all  grades  from 
coarse  cubes  to  extremely  fine  granular,  and  sometimes  lam- 
ellar. The  percentage  of  silver  it  carries  varies  from  a  few 
ounces  to  several  hundred  ounces  per  ton. 

Garnet.  —  Large  brown  garnets  are  occasionally  found  im- 
beded  in  granite  on  Griffith  Mountain. 

Gibralter  Rock.  —  A  ledge  of  this  variety  of  limestone  is 
located  near  Idaho  Springs.  When  polished  it  is  quite  hand- 
some. 

Hematite.  —  Ocherous  hematite  is  found  near  the  surface 
of  many  of  the  veins. 

Hornblende.  —  Of  general  occurrence  in  the  granitic  rocks. 
An  essential  constituent  of  syenite,  and  is  frequently  found 
massive.  No  good  crystals  have  been  found. 

Hornstone.  —  Of  frequent  occurrence  in  the  mines,  forming 
part  of  the  gangue  rock. 

Kaolinite  (porcelain  clay).  —  Masses  showing  crystalline 
structure  in  the  Silver  Mountain  lode,  near  Empire.  Occurs 
in  many  other  lodes  in  small  quantity. 

Linarite  (cupreous  anglesite).  —  A  mineral  having  the  gen- 
eral characteristics  of  linarite  is  found  at  the  surface  of  some 
of  the  lodes  on  Red  Elephant  Mountain. 

Magnetite  (magnetic  iron).  —  Crystals  of  magnetite  are  of 
frequent  occurrence  in  granite.  The  granite  quarried  at 
Brownville  is  liberally  sprinkled  with  crystals  of  this  mineral. 

Malachite  (green  carbonate  of  copper).  —  Occurs  as  a  stain 
or  incrustation  at  the  surface  of  man  of  the  veins. 


.—  Found  in  small  quantities  at  the  surface,  of  the 
Colorado  Central  vein. 

« 


1  /I 


4  Clear  Creek  County  Minerals: 

Micaceous  Iron  (hematite). — Quite  abundant  between  Clear 
Creek  and  Mill  Creek. 

Molybdenite. — Small  masses  in  the  Louisiana  lode,  Sher- 
man Mt. ,  in  the.  Colorado  Central  mine,  in  the  Moline  Tun- 
nel, in  several  localities  on  Red  Elephant  Mt. ,  and  in  Daily 
District. 

Muscovite  (corfUnon  mica). — Common  in  archean  rocks. 
Sometimes  found  in  large  masses.  Very  good  crystals  are 
found  in  a  mica  claim  near  Graymont. 

Native  Copper. — Small  dendritic  scales  in  the  Centennial 
and  McClellan  mines ;  wires  and  small  masses  in  the  Pitts- 
burg  mine,  Empire.  Loose  masses  have  been  found  in  the 
soil  about  Idaho. 

Native  Gold. — -In  placers  and  in  Veins  along  the  creek 
from  Idaho  to  Empire,  on  Fall  River  and  in  Argentine  Dis- 
trict. Many  of  the  silver  mines  also  carry  an  appreciable 
amount  of  gold. 

Native  Silver. — In  leaf  and  wire  form  in  many  of  the  mines 
throughout  the  county.  Nuggets  in  the  talc  bed  on  Fall 
River. 

Niccolite  (arsenical  nickel). — Occurs  sparingly  in  the  Rosa 
lode,  Dumont. 

Orthoclase  (common  feldspar). — One  of  the  most  common 
rocks  throughout  the  county  and  occurs  in  immense  masses 
as  well  as  a  constituent  of  nearly  all  country  rock. 

Polybasite. — Next  to  gray  copper  polybasite  is  the  most 
abundant  rich  silver  ore  found  in  the  county.  Crystals  are 
quite  abundant  in  the  Emma  mine,  and  some  have  been 
found  more  than  an  inch  in  their  longest  diameter.  A  few 
crystals  are  met  with  in  the  Colorado  Central.  It  usually 
occurs  massive,  when  it  is  difficult  to  distinguish  from  gray 
copper. 

Proustite  (light  ruby  silver  ore). — Small  masses  and  mi- 
nute translucent  crystals  in  the  Colorado  Central  mine. 

Pyrargyrite  (dark  ruby  silver  ore). — Of  general  occurrence 
in  the  silver  mines  but  usually  in  small  quantity.  Probably 
more  is  found  in  the  Colorado  Central  than  in  any  other 
mine.  Crystals  have  never  been  noticed. 

Pyrite. — Almost  universally  in  the  mines.  Particularly 
abundant  at  Empire  and  Idaho,  and  in  the  "gold  belt"  lodes 
at  Georgetown.  Usually  massive  ;  crystals  quite  small  and 
rarely  vary  from  the  cube.  Carries  gold  and  a  little  silver. 


Clear  Creek  County  Minerals.  5 

Pyromorphite  (phosphate  of  lead). — Sparingly  in  some  of 
the  mines  on  Democrat  Mountain. 

Quarts. — In  large  masses  at  the  eastern  end  of  the  county. 
Forms  part  of  the  gangue  rock  of  the  mines.  Crystals  fre- 
quent but  usually  small. 

Rhodochrosite  (carbonate  of  manganese). — Some  very  pretty 
crystals  are  found  in  the  Danube  lode,  near  Idaho  Springs. 

Rose  Quarts. — Beautiful  rose-tinted  masses  on  Floyd  Hill. 
Crystals  in  the  Little  Giant  mine. 

Schirmerite  (bismuth  silver  ore). — In  small  masses  in  the 
mines  of  Geneva  District. 

Siderite  (carbonate  of  iron). — Of  frequent  occurrence,  both 
massive  and  crystallized,  in  the  mines  in  the  Trail  Creek  re- 
gion. Occasionally  in  other  mines. 

Sphalerite  (zinc  blende). — Abundant,  especially  in  the 
Georgetown  and  Silver  Plume  district.  Varies  in  color  from 
amber  to  black.  Large  clusters  of  black  crystals  in  the  Maine 
mine,  some  crystals  three  inches  in  diameter.  Usually  car- 
ries but  littje  silver. 

Stromeyerite. — A  variety  carrying  a  little  more  than  one 
per  cent  of  silver  is  found  in  small  quantities  in  the  Algon- 
quin, Silent  Friend  and  other  lodes  on  Saxon  Mountain. 
In  large  quantities  in  the  Plutus  mine,  mixed  with  bornite, 
and  carrying  25  per  cent  of  silver.  In  small  acicular  crystals 
in  the  Little  Giant  mine,  and  carrying  about  50  per  cent  of 
silver. 

Talc. — An  extensive  bed  near  the  head  of  Fall  River  which 
is  being  sluiced  by  the  Alice  company  for  the  gold  it  contains. 

Tennantite  (arsenical  sulphide  of  copper). — Clusters  of 
highly  polished  crystals  from  microscopic  size  to  ^  of  an  inch 
in  diameter  in  the  Freeland  mine. 

Tourmaline. — Inferior  tourmaline  is  found  on  Baker  Moun- 
tain and  near  Green  Lake. 

Tetrahedrite  (gray  copper). — The  most  abundant  rich  silver 
ore.  Gray  copper  from 'the  mines  in  the  vicinity  of  George- 
town and  Silver  Plume  carries  as  high  as  30  per  cent  of  silver, 
while  that  from  the  mines  east  of  Georgetown  and  in  the 
vicinity  of  Idaho  Springs,  and  in  Geneva  District  rarely  con- 
tains more  than  one  per  cent  of  silver.  A  few  coarse  crystals 
have  been  found  in  the  Geneva  District  mines. 

Uraninite  (pitchblende). — Small  masses  have  been  found 
in  the  Jo  Reynolds  mines. 


Gilpin   County  Minerals, 
GILPIN   COUNTY   MINERALS. 


Albite  (soda  feldspar). — A  constituent  of  some  of  the  arch  - 
ean  rocks. 

Amethyst. — Small  beautiful  crystals  of  good  color  have 
been  found  in  the  gravel  in  Nevada. 

Arsenopyrite  (arsenical  pyrites). — Occasionally  found  in 
small  masses  in  the  Kansas,  Illinois,  Burroughs,  California 
and  other  mines. 

Azurite  (blue  carbonate  of  copper.) — Occurs  as  an  incrus- 
tation or  stain  at  the  surface  of  many  of  the  mines. 

Barite  (heavy  spar). — Of  frequent  occurrence  in  some  of 
the  mines,  and  occasionally  crystallized. 

v  Biotite  (black  mica). — A  constituent  of  much  of  the  gran- 
ite and  eruptive  rocks. 

Bornite  (purple  copper  ore). — Of  general  occurrence  in  the 
mines  in  greater  or  less  quantities.  Crystals  rare. . 

Calcite  (carbonate  of  lime).— Occurs  in  small  quantities 
in  many  of  the  mines. 

Chalcanthite  (blue  vitriol). — Near  Black  Hawk,  in  a  de- 
posit. In  many  of  the  old  mine  dumps  about  Central. 

Chalcedony. — Small  masses  occasionally  met  with  in  many 
of  the  mines. 

Chalcopyrite  (copper  pyrites). — Of  general  occurrence  and 
one  of  the  principal  ores  of  gold.  Crystals  frequent. 

Covellite  (indigo  copper). — In  grains  and  as  a  powder  in- 
Pewabic,  Gunnell,  Sapp  and  other  lodes  near  Central. 

Enargite  (arsenical  sulphide  of  copper). — Massive  and  finely 
crystallized  in  the  Powers  mine,  Russell  District. 

Epidote. — Massive  and  crystallized  in  the  granitic  rocks 
throughout  the  county. 

Float  Stone. — Snow-white  masses  showing  gold  have  been 
taken  from  the  Mammoth  mine,  Central. 

Fluorite  (fluor  spar). — Met  with  occasionally  in  some  of 
the  veins. 

Galenite. — Abundant  in  many  of  the  mines.  Fine  crystal- 
lized specimens  have  been  found  in  the  Glennan  and  Running 
mines,  Black  Hawk,  the  Delaware  and  Calhoun  lodes,  Rus- 
sell District,  the  Mount  Desert  and  Forks  lodes  at  Nevada. 
Crystal  two  inches  across  have  been  found  in  the  Glennan. 


Gilpin   County  Minerals.  j 

Garnet. — Iron  garnets  are  quite  abundant  in  the  vicinity 
of  Central. 

Hornblende.- — Of  general  occurrence  in  the  archean  rocks. 

Hornstone. — Of  frequent  occurrence  in  the  mines,  forming 
part  of  the  gangue  rock. 

Kaolinite  (porcelain  clay). — In  greater  or  less  abundance 
in  all  the  mines. 

Magnetite  (magnetic  iron). — Crystals  of  magnetite  are  of 
frequent  occurrence  in  granite.  Octahedral  crystals  on  Gun- 
nell  Hill. 

Malachite  (green  carbonate  of  copper). — Occurs  as  a  stain 
or  incrustation  at  the  surface  of  many  of  the  veins. 

Melanterite  (copperas,  green  vitriol). — In  the  dumps  of 
many  of  the  old  mines. 

Molybdenite. — Small  masses  in  the  Leavitt  lode. 

Muscovite  (common  mica). — Common  in  archean  rocks. 
Sometimes  found  in  large  masses. 

Oligoclase  (aveuturine  feldspar). — A  constituent  of  much  of 
the  archean  rocks. 

Native  Copper.— Small  dendritic  coatings  in  a  number  of 
the  lodes.  Masses  weighing  several  pounds  have  been  found 
in  the  Narraganset  and  Gregory  mines. 

Native  Gold. — In  placers  and  in  the  veins.  Beautiful  mi- 
crosopic  crystals  in  the  Gunnell,  Gregory,  Bates  and  other 
mines.  Strings  of  minute  crystals,  forming  chain-like  wires, 
are  frequently  found. 

Native  Silver. — In  leaf  and  wire  form  in  the  Coaley  and 
other  mines. 

Orthoclase  (common  feldspar). — One  of  the  most  common 
rocks  throughout  the  county  and  occurs  in  immense  masses 
as  well  as  a  constituent  of  nearly  all  of  the  rocks.  Crystals 
in  porphyry  on  Gregory  Hill. 

Pyrite  (iron  pyrites). — Abundant,  massive  and  crystallized, 
in  all  the  lodes,  and  composes  the  greater  part  of  the  gold 
ore.  Beautiful  crystallized  specimens  and  radiated  and  bo- 
tryoidal  masses  common  in  many  of  the  mines.  Cubes  from 
one  to  three  inches  across  have  been  taken  from  the  King- 
ston, Hill  House  and  S.  P.  Chase  lodes  in  Russell  District. 
A  lode  near  the  head  of  Virginia  Canon  has  furnished  a  great 
many  modified  crystals. 

Rose  Quarts. — In  small  masses  in  the  vicinity  of  Central 
and  other  localities. 


8  Gilpin   County  Minerals. 

Quartz. — Common  in  large  masses.  Forms  part  of  the 
gangue  rock  in  the  mines.  Crystals  frequent  but  usually 
small.  An  essential  constituent  of  granitic  rocks. 

Siderite  (carbonate  of  iron).  — Of  frequent  occurrence,  both 
massive  and  crystallized,  in  the  mines. 

Rock  Crystal. — Doubly  terminated  limpid  crystals  common 
in  the  gravel  on  Quartz  Hill.  The  crystals  are  small  but 
quite  perfect. 

Sphalerite  (zinc  blende). — Abundant  in  many  of  the  lodes. 
Clusters  of  tetrahedral  crystals  in  the  Coaley  lode,  Black 
Hawk.  Crystallized  in  the  Delaware  and  Calhoun  lodes. 

Talc. — In  small  quantities  in  nearly  all  the  mines. 

Tourmaline. — Black  crystals  near  Nevada. 

Tetrahedrite  (gray  copper). — Not  unfrequently  found  in  a 
number  of  mines,  sometimes  crystallized. 

Uraninite  (pitchblende). — Abundant  at  one  time  in  the 
Wood  lode,  L/eavenworth  Gulch.  A  few  imperfect  crystals. 

Uraconite. — Occurs  as  a  yellow  coating  on  pitchblende  in 
the  Wood  lode. 

Cerussite  (carbonate  of  lead). — Of  rare  occurrence  at  the 
surface  of  some  of  the  veins. 

Lepidomelane  (iron  potash  mica). — A  constituent  of  some  of 
the  granite. 

NEEDS  VERIFICATION. 

Aurichalcite. — Jones  lode,  near  Nevada. 

Allophane. — Cincinnati  lode. 

Calamine. 

Glockerite. — On  old  dumps. 

Goslarite. — Wood  lode,  Leavenworth  Gulch. 

Greenockite. — Jones  and  Dallas  lodes. 

Jarosite. — Wood  lode. 

Lievrite. — Below  Black  Hawk. 

Magnesite. — Bobtail,  Running  and  Pewabic  lodes. 

Marcasite. 

Native  Sulphur. — Jones  lode,  Nevada. 

Plumbogummite.— \32ti\as  lode,  Black  Hawk. 

Pyrrhotite. 

Smithsonite. — Jones  lode,  Nevada. 

Uranochalcite. — Wood  lode. 

Willemite. — Jones  lode,  Nevada. 

Wulfenite.— Gunnell  Hill. 

Zincite. — Jones  lode,  Nevada. 

Zippeite. — Wood  lode. 


Grand  County  Minerals. 
GRAND   COUNTY   MINERALS. 


Albite  (soda  feldspar). — A  constituent  of  some  of  the  arch- 
aean  rocks. 

Agate. — Abundant  along  Williams  River;  on  the  ridge  be- 
tween Hot  Sulphur  Springs  and  Corral  Creek  ;  on  the  moun- 
tains at  the  mouth  of  Willow  Creek. 

Agatized  Wood.  — Abundant  on  the  ridges  north  of  Willow 
Creek.  Also  between  Hot  Springs  and  Corral  Creek. 

Argentite  (silver  glance). — In  small  quantities  in  the  min- 
eral veins  in  Campbell  district. 

Azurite  (blue  carbonate  of  copper.) — Occurs  as  an  incrus- 
tation in  copper  veins  in  the  Park  Range  at  the  head  of  a  fork 
of  the  North  Plate  River. 

Barite  (heavy  spar). — Reported  to  occur  in  extensive  beds 
on  Vasquez  Creek. 

Basanite  (touch  stone). — Sparingly  along  Willow  Creek. 

Biotite  (black  mica). — A  constituent  of  much  of  the  gran- 
ite and  dike  rocks  of  the  mountains  and  eruptive  rocks  of  Mid- 
dle Park. 

Bismutite  (carbonate  of  bismuth). — Found  near  Cummuns 
City,  North  Park.  Needs  verification. 

Brown  Coal  (lignite). — Extensive  veins  in  North  Park  and 
exists  at  various  points  on  the  divide  between  North  and  Mid- 
dle Parks. 

Byerite. — A  name  given  to  the  coal  found  in  Middle  Park. 
It  belongs  to  the  class  caking  bituminous,  and  resembles  al- 
bertite  in  the  large  amount  of  gas  and  tarry  oil  yielded.  It 
melts  and  intumesces  when  heated. 

Carnelian. — Sparingly  on  the  ridge  south  of  Willow  Creek. 

Cerussite  (carbonate  of  lead). — Frequently  found  in  small 
masses  near  the  surface  of  mineral  veins. 

Chalcedony. — Abundant  on  the  ridges  on  both  sides  of 
Willow  Creek.  Common  on  the  ridge  between  Hot  Springs 
and  Corral  Creek. 

Chalcocite  (copper  glance,  sulphuret  of  copper). — In  copper 
veins  in  the  Park  Range.  Bancroft  Library 

Chalcopyrite  (copper  pyrites). — Of  general  occurrence  in 
small  quantities  in  the  mines. 


TO  Grand  County  Minerals. 

Chrysoprase. — Sparingly  in  geodes  on  upper  Grand    River. 

Cuprite  (red  oxide  of  copper). — In  copper  veins  in  the  Park 
Range. 

Cyanite. — Occurs  in  the  quartzite  of  Medicine  Bow  Peak. 
Epidote. — Massive   and  crystallized  in  the  granitic  rocks. 

Galenite. — Abundant  in  many  of  the  mines.  Massive  veins 
near  the  head  of  Troublesome  Creek. 

Heliotrope  (bloodstone). — Fine  specimens  occasionally  met 
with  in  the  vein  of  green  jasper  on  the  hill  at  the  junction  of 
Willow  Creek  and  Grand  River. 

Hornblende. — Of  general  occurrence  in  the  archaean  rocks. 

Hypersthene. — A  constituent  of  the  feldspar  basalt  from 
Grand  River,  above  Hot  Springs. 

Jasper. — Veins  of  green,  red  and  yellow  jasper  on  the  hill 
at  the  junction  of  Willow  Creek  and  Grand  River.  Ribbon 
jasper  is  quite,  common  at  this  locality.  Red  and  yellow  jas- 
per is  more  or  less  abundant  on  the  ridges  along  Willow 
Creek,  in  the  vicinity  of  Hot  Springs,  and  in  the  streams. 

Lepidomelane  (iron  potash  mica). — A  constituent  of  some  of 
the  granite. 

Magnetite  (magnetic  iron). — An  accessory  mineral  of  much 
of  the  granite. 

Malachite  (green  carbonate  of  copper). — Occurs  as  a  stain 
or  incrustation  at  the  surface  of  many  of  the  copper  veins  in 
the  Park  Range. 

Moss  Agate. — Quite  abundant  on  the  south  side  of  Williams 
River,  three  or  four  miles  from  the  Grand. 

Mottled  Agate. — On  Williams  River;  in  the  vicinity  of 
Hot  Springs  ;  Willow  Creek,  and  numerous  other  localities. 

Muscovite  (common  mica). — Common  in  archsean  rocks> 
frequently  occurring  in  large  masses. 

Native  Bismuth.— Occurs  in  small  particles  in  bismutite  at 
Cummuns  City.  The  find  is  not  satisfactorily  verified. 

Native  Gold. — In  the  alluvium  of  Willow  Creek. 

Native  Silver. — In  leaf  and  wire  form  in  some  of  the  silver- 
bearing  veins. 

Oligoclase  (aventurine  feldspar).— A  constituent  of  much  of 
the  archsean  rocks. 

Onyx. — Sparingly  with  chalcedony  on  the  ridge  south  of 
of  Willow  Creek. 


Jefferson  County  Minerals,  ri 

Orthoclase  (common  feldspar). — The  most  abundant  con- 
stituent of  the  archsean  rocks. 

Plasma. — Occurs  in  geodes  found  on  upper  Grand  River. 

Pyrargyrite  (dark  ruby  silver  ore). — In  small  quantities  in 
the  lodes  of  Campbell  district. 

Pyrile  (iron  pyrites). — More  or  less  abundant  in  the  min-f 
eral  veins. 

Pyroxene. — Next  to  the  feldspars,  pyroxene  is  the  most 
universal  constituent  of  the  igneous  rocks. 

Quartz. — Common,  in  crystal,  small  masses  and  a  constitu- 
ent of  metamorphic  and  sedimentary  rocks. 

Sardonyx. — Fine  specimens  occasionally  met  with  on  the 
ridge  south  of  Willow  Creek,  a  mile  or  two  from  the  Grand. 

Stibnite  (antimony  glance). — Float  masses  of  stibnite  and 
quartz,  two  feet  in  thickness,  are  found  between  the  head  of 
Troublesome  Creek  and  Lost  Lake. 

Sphalerite  (zinc  blende). — Abundant  in  many  of  the  lodes. 

Tetrahedrite  (gray  copper). — Not  unfrequently  found  in 
the  mines  at  Lulu. 


JEFFERSON   COUNTY   MINERALS. 


Actinolite. — Columnar  masses  of  green  color  near  Bergen 
ranch  on  Bear  Creek,  and  at  the  entrance  of  Coal  Creek  canon. 

Agate. — Mottled  agate  common  on  Green  Mountain. 

Agatized  Wood. — Abundant  on  Table  Mountains. 

Alabaster. — Massive  white  and  mottled  alabaster  in  Jurassic 
shales  near  Morrison. 

Albite  (soda  feldspar). — A  constituent  of  some  of  the  arch- 
sean  rocks. 

Allophanc. — Forms  a  thin  bluish  crust  on  limonite  in  veins 
near  Bergen  ranch,  Bergen  Park. 

Amazonstonc. — On  Elk  Creek  and  near  the  mouth  of  Tar- 
ryall  Creek,  with  smoky  quartz  and  gothite. 

Analdte. — Pure  white  or  transparent  crystals  in  the  basalt 
of  North  Table  Mountain,  associated  with  other  zeolite  min- 
erals. Specially  abundant  on  the  east  side  of  the  mountain. 
Small  crystals  abundant  on  South  Table  Mountain. 


12  Jefferson  Coimty  Minerals. 

Apophyllite. — Well  developed  crystals  of  prismatic  habit  on 
North  Table  Mountain.  The  larger  crystals  are  usually  ter- 
minated by  a  number  of  small  pyramids. 

Aquamarine. — Small  inferior  specimens  on  Tiffany  ranch, 
Bear  Creek. 

Aragonite. — Occurs  in  a  vein  at  Golden  Gate. 

Asphaltum  (bitumen,  mineral  pitch).  —  Forms  crusts  on 
sandstone  near  Morrison. 

Attgite. — An  essential  constitiient  of  the  augite-andesite 
rocks  of  Green  and  Table  Mountains. 

Azurite  (blue  carbonate  of  copper.) — Occurs  as  an  incrus- 
tation and  minute  crystals  in  the  copper  veins,  Bear  Creek. 

Beryl. — Abundant  on  Bear  Creek  and  in  Bergen  Park. 
Crystals  vary  in  size  from  small  ones  to  those  two  feet  in  di- 
ameter. Translucent  and  good  color  specimens  rare. 

•Biotite  (black  mica). — A  constituent  of  much  of  the  gran- 
ite and  dike  rocks. 

Bismutite  (carbonate  of  bismuth). — In  the  Bismuth  Queen 
vein  on  Guy  Hill. 

Bismuthinite  (sulphuret  of  bismuth). — Associated  with  bis- 
mutite  in  the  Bismuth  Queen  lode,  Guy  Hill. 

Bole  (iron  clay). — Occurs  as  a  dark  brown  clay  on  South 
Table  Mountain. 

Brown  Coal  (lignite). — Extensive  veins  at  Golden,  on  Ral- 
ston Creek,  and  other  localities. 

Calcite  (carbonate  of  lime). — Large  masses  of  cleaveable 
white  calcite  on  Bear  Creek. 

Cairngorm  (smoky  quartz.) — On  Elk  Creek  and  near  the 
mouth  of  Tarryall  Creek,  with  amazonstone  and  gothite. 

Carnelian. — Small  pieces  of  red  and  yellow  carnelian  on 
Green  Mountain. 

Chabasite. — Abundant  in  small  crystals  in  the  basalt  of 
North  Table  Mountain. 

Chalcedony. — Sparingly  on  Green  Mountain  and  vicinity. 

Chalcedony x. — Sparingly  between  the  mountains  and  Den- 
ver. 

Chalcocite  (copper  glance,  sulphuret  of  copper). — In  copper 
lodes  on  Bear  Creek,  in  Bergen  Park,  and  near  Golden. 

Chalcopyrite  (copper  pyrites). — In  the  mineral  veins  on 
Bear  Creek  and  in  Bergen  Park. 


fefferson  County  Minerals.  /j 

Chlorophane  (green  fluor  spar). — Abundant  in  many  veins 
on  Bear  Creek. 

Chrysocolla  (silicate,  of  copper).— Sparingly  in  the  copper 
veins  on  Bear  Creek  and  in  Bergen  Park. 

Cohimbite. — In  small  masses  011  Turkey  Creek.  Analysis 
shows  the  mineral  to  contain  a  small  amount  of  tin  and  n 
per  cent  of  manganese. 

Cuprite  (red  oxide  of  copper). — In  copper  veins  in  Bergen 
Park  and  on  Bear  Creek. 

Enstatite. — An  accessory  mineral  of  a  -dike  of  diabase  at 
Morrison. 

Epidote. — Massive  and  crystallized  in  the  granitic  rocks. 
Quite  pretty  crystals  are  found  on  Bear  Creek. 

Fluorite  (fluor  spar). — Massive,  purple,  green  and  white, 
in  veins  on  Bear  Creek.  Purple  near  the  mouth  of  Tarry  all. 
Massive  on  Cub  Creek. 

Galenite. — Abundant  in  many  of  the  veins  on  Bear  Creek. 

Garnet. — Iron  garnets  are  quite  common  in  Bergen  Park. 

Gothite. — On  Elk  Creek  and  near  the  mouth  of  Tarry  all 
Creek,  with  amazonstone  and  smoky  quartz. 

Gypsum. — Abundant  in  Jurassic  shale  near  Morrison. 

Hematite. — An  earthy  red  hematite  at  Morrison. 

Henlandite. — Small  colorless  tabular  crystals  in  the  augite- 
andesite  of  Green  Mountain. 

Hornblende. — Of  general  occurrence  in  the  archsean  rocks. 

Iceland  Spar. — Small  yellowish  masses  in  the  amygdaloid 
of  the  Table  Mountains. 

Jasper. — Red  and  yellow  jasper  in  the  Green  Mountain 
region. 

Kaolinite   (porcelain    clay). — Extensive  beds  at  Golden. 

Laumontite. — Occurs  as  a  reddish-yellow  sand-like  material 
and  in  compact  masses  in  the  basalt  of  North  Table  Mt. 

Lepidomelane  (iron  potash  mica). — A  constituent  of  some  of 
the  granite. 

Levynite. — Of  rare  occurrence  in  small  white  and  colorless 
crystals  associated  with  other  zeolites  on  North  Table  Mt. 

Limonite. — Small  masses  in  the  veins  of  Bergen  Park. 

Magnetite  (magnetic  iron). — An  accessory  mineral  of  much 
of  the  granite.  Loose  crystals  in  the  soil  on  Bear  Creek  and 
in  Bergen  Park. 


14  Jefferson  £onnty.  Miner alsi  ..-.:. 

Malachite  (green  carbonate  of  copper). — Occurs  as  a  stain 
or  incrustation  at  the  surface  of  many  of  the  copper  veins  in 
Bergen  Park  and  on  Bear  Creek. 

Mesolite. — Occurs  as  exceedingly  delicate  needles  in  the 
basalt  of  North  Table  Mountain. 

Microcline. — Near  the  mouth  of  Tarryall  Creek,  with  ama- 
zonstone,  smoky  quartz,  gothite  and  fluorite. 

Mineral  Resin. — Small  specimens  of  an  undetermined  va- 
riety of  resin  in  the  soil  on  South  Table  Mountain  and  in  the 
coal  veins. 

Molybdenite. — Occurs  as  an  associate  of  bismuth  minerals 
on  Guy  Hill. 

Muscovite,  (common  mica). — Common  in  archaean  rocks, 
Large  deposits  on  Deer  Creek,  where  some  mica  mining  has 
been  done. 

Native  Alum. — In  Jurassic  shale  on  Bear  Creek  near  Mor- 
rison, and  between  Morrison  and  Platte  Canon. 

Native  Copper. — In  considerable  quantities  in  copper  lodes 
near  Golden.  Small  specimens  in  the  lodes  on  Bear  Creek 
and  in  Bergen  Park. 

Native  Gold. — In  the  alluvium  of  Clear  Creek. 

Native  Sulphur. — In  small  crystals.  Exact  locality  not 
known. 

Natron  (carbonate  of  soda). — As  crusts  and  in  solution  in 
the  waters  of  the  lakes  between  Turkey  and  Bear  Creeks. 

Natrolite.- — Occurs  as  delicate  prisms  sparingly  deposited 
on  analcite  or  associated  with  that  mineral  in  the  basalt  of 
South  Table  Mountain.  Less  frequently  on  North  Table  Mt. 

Oligoclase  (aventurine  feldspar). — A  constituent  of  much  of 
the  archaean  rocks. 

Orthoclase  (common  feldspar). — The  most  abundant  con- 
stituent of  the  archaean  rocks. 

Petroleum. — Oozes  from  Cretaceous  sandstone  at  Morrison. 

Plagioclase. — An  essential  constituent  of  diabase  from  Mor- 
rison, in  which  it  occurs  in  narrow  prisms. 

Ptilolite  (new). — A  new  zeolite  described  by  Whitman  Cross. 
Occurs  in  small  white  tufts  in  the  augite-andesite  of  Green 
Mountain.  Sparingly  with  other  zeolites  on  the  Table  Mts. 

Pyrite  (iron  pyrites). — Small  quantities  in  the  veins  of 
Bergen  Park  and  on  Bear  Creek. 


Jefferson  County  Minerals.  75 

Pyroxene. — An  essential  constituent  of  diabase  from  a  dike 
near  Morrison. 

Quartz. — Large  veins  and  masses  of  white  quartz  in  Bergen 
Park,  on  Bear  Creek,  and  in  the  Guy  Hill  region. 

Rock  Crystal. — Colorless  quartz  in  crystals  abundant  on 
the  divide  between  Deer  and  Elk  Creeks. 

Rose  Quarts. — In  large  masses  in  Bergen  Park. 

Satin  Spar  (var.  gypsum). — Abundant  in  Jurassic  shales 
near  Morrison. 

Scolecite. — Occurs  sparingly  in  spheres  with  a  radiate  struct- 
ure in  the  basalt  of  North  Table  Mountain. 

Selenite  (gypsum). — In  Jurassic  shale  near  Morrison. 

Silicified  Wood. — On  South  Table  Mountain.  Silicified 
palm  wood  abundant  between  Golden  and  Denver. 

Stilbite. — Sparingly  in  small  clear  crystals  with  other  zeo- 
lites on  North  Table  Mountain. 

Thenardite  (sulphate  of  soda). — Occurs  in  quantity  at  Burd- 
sall's  lake  near  Morrison. 

Thomsonite. — In  the  basalt  of  North  Table  Mountain  in 
minute  rectangular  blades  which  are  placed  like  a  closed  fan, 
and  in  spherical  concretions  having  a  radiate  structure. 

Tourmaline. — Fine  black  crystals  in  quartz  on  Bear  Creek. 
Near  the  head  of  Ralston  Creek. 


Jefferson  County  is  also  accredited  with  the  following  min- 
erals, btit  their  occurrence  needs  verification  : 
Aluminite,  Mt.  Vernon. 
Antrimolite,  Table  Mountains. 
Egeran,  Gennessee  ranch  on  Bear  Creek. 
Idocrase,  Bear  Creek. 
Pyrrhotite. 

Wavellite,  Table  Mountains. 
Wheelerite,  in  the  coal. 
Topazolite,  Malachite  lode,  Bear  Creek. 


